Start replacing write_custom_data with the attribute exporter.

Instances are read as linked duplicates of the source object.

source/blender/blenkernel/BKE_attribute.h

@@ -49,6 +49,14 @@ struct CustomDataLayer *BKE_id_attribute_find(const struct ID *id,
                                               int type,
                                               AttributeDomain domain);
 
+/* Return an existing CustomDataLayer, or create a new one if none is found for the given
+ * parameters and return it. */
+struct CustomDataLayer *BKE_id_attribute_ensure(struct ID *id,
+                                                const char *name,
+                                                const int type,
+                                                const AttributeDomain domain,
+                                                struct ReportList *reports);
+
 AttributeDomain BKE_id_attribute_domain(struct ID *id, struct CustomDataLayer *layer);
 int BKE_id_attribute_data_length(struct ID *id, struct CustomDataLayer *layer);
 bool BKE_id_attribute_required(struct ID *id, struct CustomDataLayer *layer);
@@ -65,6 +73,13 @@ int *BKE_id_attributes_active_index_p(struct ID *id);
 
 CustomData *BKE_id_attributes_iterator_next_domain(struct ID *id, struct CustomDataLayer *layers);
 
+typedef struct DomainInfo {
+  CustomData *customdata;
+  int length;
+} DomainInfo;
+
+void BKE_id_attribute_get_domains(const struct ID *id, DomainInfo info[ATTR_DOMAIN_NUM]);
+
 #ifdef __cplusplus
 }
 #endif

source/blender/blenkernel/BKE_cachefile.h

@@ -11,6 +11,7 @@
 extern "C" {
 #endif
 
+struct CacheAttributeMapping;
 struct CacheFile;
 struct CacheFileLayer;
 struct CacheReader;
@@ -63,6 +64,17 @@ struct CacheFileLayer *BKE_cachefile_get_active_layer(struct CacheFile *cache_fi
 
 void BKE_cachefile_remove_layer(struct CacheFile *cache_file, struct CacheFileLayer *layer);
 
+struct CacheAttributeMapping *BKE_cachefile_add_attribute_mapping(struct CacheFile *cache_file,
+                                                                  const char *name,
+                                                                  int mapping_type,
+                                                                  int domain);
+
+struct CacheAttributeMapping *BKE_cachefile_get_active_attribute_mapping(
+    struct CacheFile *cache_file);
+
+void BKE_cachefile_remove_attribute_mapping(struct CacheFile *cache_file,
+                                            struct CacheAttributeMapping *mapping);
+
 #ifdef __cplusplus
 }
 #endif

source/blender/blenkernel/BKE_modifier.h

@@ -601,6 +601,10 @@ void BKE_modifier_blend_read_data(struct BlendDataReader *reader,
                                   struct Object *ob);
 void BKE_modifier_blend_read_lib(struct BlendLibReader *reader, struct Object *ob);
 
+/* Return whether the modifier can operate directly on a Curve, i.e. without needing a conversion
+ * to a temporary Mesh. */
+bool BKE_modifier_supports_curve_data(const ModifierData *md);
+
 #ifdef __cplusplus
 }
 #endif

source/blender/blenkernel/BKE_pointcloud.h

@@ -25,6 +25,9 @@ extern const char *POINTCLOUD_ATTR_RADIUS;
 void *BKE_pointcloud_add(struct Main *bmain, const char *name);
 void *BKE_pointcloud_add_default(struct Main *bmain, const char *name);
 struct PointCloud *BKE_pointcloud_new_nomain(int totpoint);
+void BKE_pointcloud_nomain_to_pointcloud(struct PointCloud *pointcloud_src,
+                                         struct PointCloud *pointcloud_dst,
+                                         bool take_ownership);
 
 struct BoundBox *BKE_pointcloud_boundbox_get(struct Object *ob);
 bool BKE_pointcloud_minmax(const struct PointCloud *pointcloud, float r_min[3], float r_max[3]);

source/blender/blenkernel/intern/attribute.c

@@ -29,12 +29,7 @@
 
 #include "RNA_access.h"
 
-typedef struct DomainInfo {
-  CustomData *customdata;
-  int length;
-} DomainInfo;
-
-static void get_domains(const ID *id, DomainInfo info[ATTR_DOMAIN_NUM])
+void BKE_id_attribute_get_domains(const ID *id, DomainInfo info[ATTR_DOMAIN_NUM])
 {
   memset(info, 0, sizeof(DomainInfo) * ATTR_DOMAIN_NUM);
 
@@ -87,7 +82,7 @@ static void get_domains(const ID *id, DomainInfo info[ATTR_DOMAIN_NUM])
 static CustomData *attribute_customdata_find(ID *id, CustomDataLayer *layer)
 {
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
 
   for (AttributeDomain domain = 0; domain < ATTR_DOMAIN_NUM; domain++) {
     CustomData *customdata = info[domain].customdata;
@@ -102,7 +97,7 @@ static CustomData *attribute_customdata_find(ID *id, CustomDataLayer *layer)
 bool BKE_id_attributes_supported(struct ID *id)
 {
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
   for (AttributeDomain domain = 0; domain < ATTR_DOMAIN_NUM; domain++) {
     if (info[domain].customdata) {
       return true;
@@ -136,7 +131,7 @@ CustomDataLayer *BKE_id_attribute_new(
     ID *id, const char *name, const int type, const AttributeDomain domain, ReportList *reports)
 {
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
 
   CustomData *customdata = info[domain].customdata;
   if (customdata == NULL) {
@@ -212,7 +207,7 @@ CustomDataLayer *BKE_id_attribute_find(const ID *id,
                                        const AttributeDomain domain)
 {
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
 
   CustomData *customdata = info[domain].customdata;
   if (customdata == NULL) {
@@ -229,10 +224,22 @@ CustomDataLayer *BKE_id_attribute_find(const ID *id,
   return NULL;
 }
 
+CustomDataLayer *BKE_id_attribute_ensure(
+    ID *id, const char *name, const int type, const AttributeDomain domain, ReportList *reports)
+{
+  CustomDataLayer *layer = BKE_id_attribute_find(id, name, type, domain);
+
+  if (layer) {
+    return layer;
+  }
+
+  return BKE_id_attribute_new(id, name, type, domain, reports);
+}
+
 int BKE_id_attributes_length(ID *id, const CustomDataMask mask)
 {
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
 
   int length = 0;
 
@@ -249,7 +256,7 @@ int BKE_id_attributes_length(ID *id, const CustomDataMask mask)
 AttributeDomain BKE_id_attribute_domain(ID *id, CustomDataLayer *layer)
 {
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
 
   for (AttributeDomain domain = 0; domain < ATTR_DOMAIN_NUM; domain++) {
     CustomData *customdata = info[domain].customdata;
@@ -265,7 +272,7 @@ AttributeDomain BKE_id_attribute_domain(ID *id, CustomDataLayer *layer)
 int BKE_id_attribute_data_length(ID *id, CustomDataLayer *layer)
 {
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
 
   for (AttributeDomain domain = 0; domain < ATTR_DOMAIN_NUM; domain++) {
     CustomData *customdata = info[domain].customdata;
@@ -300,7 +307,7 @@ CustomDataLayer *BKE_id_attributes_active_get(ID *id)
   }
 
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
 
   int index = 0;
 
@@ -325,7 +332,7 @@ CustomDataLayer *BKE_id_attributes_active_get(ID *id)
 void BKE_id_attributes_active_set(ID *id, CustomDataLayer *active_layer)
 {
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
 
   int index = 0;
 
@@ -366,7 +373,7 @@ int *BKE_id_attributes_active_index_p(ID *id)
 CustomData *BKE_id_attributes_iterator_next_domain(ID *id, CustomDataLayer *layers)
 {
   DomainInfo info[ATTR_DOMAIN_NUM];
-  get_domains(id, info);
+  BKE_id_attribute_get_domains(id, info);
 
   bool use_next = (layers == NULL);
 

source/blender/blenkernel/intern/cachefile.c

@@ -73,6 +73,7 @@ static void cache_file_copy_data(Main *UNUSED(bmain),
   cache_file_dst->handle_readers = NULL;
   BLI_duplicatelist(&cache_file_dst->object_paths, &cache_file_src->object_paths);
   BLI_duplicatelist(&cache_file_dst->layers, &cache_file_src->layers);
+  BLI_duplicatelist(&cache_file_dst->attribute_mappings, &cache_file_src->attribute_mappings);
 }
 
 static void cache_file_free_data(ID *id)
@@ -81,6 +82,7 @@ static void cache_file_free_data(ID *id)
   cachefile_handle_free(cache_file);
   BLI_freelistN(&cache_file->object_paths);
   BLI_freelistN(&cache_file->layers);
+  BLI_freelistN(&cache_file->attribute_mappings);
 }
 
 static void cache_file_foreach_path(ID *id, BPathForeachPathData *bpath_data)
@@ -110,6 +112,11 @@ static void cache_file_blend_write(BlendWriter *writer, ID *id, const void *id_a
   LISTBASE_FOREACH (CacheFileLayer *, layer, &cache_file->layers) {
     BLO_write_struct(writer, CacheFileLayer, layer);
   }
+
+  /* write attribute mappings */
+  LISTBASE_FOREACH (CacheAttributeMapping *, mapping, &cache_file->attribute_mappings) {
+    BLO_write_struct(writer, CacheAttributeMapping, mapping);
+  }
 }
 
 static void cache_file_blend_read_data(BlendDataReader *reader, ID *id)
@@ -126,6 +133,9 @@ static void cache_file_blend_read_data(BlendDataReader *reader, ID *id)
 
   /* relink layers */
   BLO_read_list(reader, &cache_file->layers);
+
+  /* relink attribute mappings */
+  BLO_read_list(reader, &cache_file->attribute_mappings);
 }
 
 IDTypeInfo IDType_ID_CF = {
@@ -464,3 +474,38 @@ void BKE_cachefile_remove_layer(CacheFile *cache_file, CacheFileLayer *layer)
   BLI_remlink(&cache_file->layers, layer);
   MEM_freeN(layer);
 }
+
+CacheAttributeMapping *BKE_cachefile_add_attribute_mapping(CacheFile *cache_file,
+                                                           const char *name,
+                                                           const int mapping_type,
+                                                           const int domain)
+{
+  const int current_mapping_count = BLI_listbase_count(&cache_file->attribute_mappings);
+
+  CacheAttributeMapping *mapping = MEM_callocN(sizeof(CacheAttributeMapping),
+                                               "CacheAttributeMapping");
+
+  if (name) {
+    BLI_strncpy(mapping->name, name, sizeof(mapping->name));
+  }
+  mapping->mapping = (char)mapping_type;
+  mapping->domain = (char)domain;
+
+  BLI_addtail(&cache_file->attribute_mappings, mapping);
+
+  cache_file->active_attribute_mapping = current_mapping_count + 1;
+  return mapping;
+}
+
+CacheAttributeMapping *BKE_cachefile_get_active_attribute_mapping(CacheFile *cache_file)
+{
+  /* BLI_findlink handles the out of bounds checks. */
+  return BLI_findlink(&cache_file->attribute_mappings, cache_file->active_attribute_mapping - 1);
+}
+
+void BKE_cachefile_remove_attribute_mapping(CacheFile *cache_file, CacheAttributeMapping *mapping)
+{
+  cache_file->active_attribute_mapping = 0;
+  BLI_remlink(&cache_file->attribute_mappings, mapping);
+  MEM_freeN(mapping);
+}

source/blender/blenkernel/intern/curves.cc

@@ -27,6 +27,7 @@
 #include "BKE_anim_data.h"
 #include "BKE_curves.hh"
 #include "BKE_customdata.h"
+#include "BKE_geometry_set.hh"
 #include "BKE_global.h"
 #include "BKE_idtype.h"
 #include "BKE_lib_id.h"
@@ -308,8 +309,15 @@ static Curves *curves_evaluate_modifiers(struct Depsgraph *depsgraph,
       continue;
     }
 
-    if ((mti->type == eModifierTypeType_OnlyDeform) &&
-        (mti->flags & eModifierTypeFlag_AcceptsVertexCosOnly)) {
+    if (mti->modifyGeometrySet) {
+      GeometrySet geometry_set = GeometrySet::create_with_curves(curves,
+                                                                 GeometryOwnershipType::ReadOnly);
+      mti->modifyGeometrySet(md, &mectx, &geometry_set);
+
+      curves = geometry_set.get_component_for_write<CurveComponent>().release();
+    }
+    else if ((mti->type == eModifierTypeType_OnlyDeform) &&
+             (mti->flags & eModifierTypeFlag_AcceptsVertexCosOnly)) {
       /* Ensure we are not modifying the input. */
       if (curves == curves_input) {
         curves = BKE_curves_copy_for_eval(curves, true);

source/blender/blenkernel/intern/displist.cc

@@ -812,12 +812,12 @@ static bool do_curve_implicit_mesh_conversion(const Curve *curve,
     return true;
   }
 
-  /* If a non-geometry-nodes modifier is enabled before a nodes modifier,
-   * force conversion to mesh, since only the nodes modifier supports curve data. */
+  /* If a modifier which does not support curve data is enabled before one that does,
+   * force conversion to mesh. */
   ModifierData *md = first_modifier;
   for (; md; md = md->next) {
     if (BKE_modifier_is_enabled(scene, md, required_mode)) {
-      if (md->type == eModifierType_Nodes) {
+      if (BKE_modifier_supports_curve_data(md)) {
         break;
       }
       return true;
@@ -874,7 +874,7 @@ static GeometrySet curve_calc_modifiers_post(Depsgraph *depsgraph,
       continue;
     }
 
-    if (md->type == eModifierType_Nodes) {
+    if (BKE_modifier_supports_curve_data(md)) {
       mti->modifyGeometrySet(md, &mectx_apply, &geometry_set);
       continue;
     }

source/blender/blenkernel/intern/modifier.c

@@ -20,6 +20,7 @@
 #include "MEM_guardedalloc.h"
 
 #include "DNA_armature_types.h"
+#include "DNA_cachefile_types.h"
 #include "DNA_cloth_types.h"
 #include "DNA_dynamicpaint_types.h"
 #include "DNA_fluid_types.h"
@@ -1518,3 +1519,27 @@ void BKE_modifier_blend_read_lib(BlendLibReader *reader, Object *ob)
     }
   }
 }
+
+bool BKE_modifier_supports_curve_data(const ModifierData *md)
+{
+  /* Sanity check. */
+  const ModifierTypeInfo *mti = BKE_modifier_get_info(md->type);
+  if (mti->modifyGeometrySet == NULL) {
+    return false;
+  }
+
+  if (md->type == eModifierType_Nodes) {
+    return true;
+  }
+
+  /* For the MeshSequenceCache, only the Alembic backend supports directly reading/modifying
+   * curves.
+   */
+  if (md->type == eModifierType_MeshSequenceCache) {
+    MeshSeqCacheModifierData *msmd = (MeshSeqCacheModifierData *)md;
+    CacheFile *cache_file = msmd->cache_file;
+    return cache_file && cache_file->type == CACHEFILE_TYPE_ALEMBIC;
+  }
+
+  return false;
+}

source/blender/blenkernel/intern/pointcloud.cc

@@ -255,6 +255,52 @@ PointCloud *BKE_pointcloud_new_nomain(const int totpoint)
   return pointcloud;
 }
 
+void BKE_pointcloud_nomain_to_pointcloud(PointCloud *pointcloud_src,
+                                         PointCloud *pointcloud_dst,
+                                         bool take_ownership)
+{
+  BLI_assert(pointcloud_src->id.tag & LIB_TAG_NO_MAIN);
+
+  /* pointcloud_src might depend on pointcloud_dst, so we need to do everything with a local copy
+   */
+  PointCloud tmp = *pointcloud_dst;
+  eCDAllocType alloctype = CD_DUPLICATE;
+
+  if (take_ownership) {
+    bool has_any_referenced_layers = CustomData_has_referenced(&pointcloud_src->pdata);
+
+    if (!has_any_referenced_layers) {
+      alloctype = CD_ASSIGN;
+    }
+  }
+
+  CustomData_reset(&tmp.pdata);
+
+  const CustomDataMask pmask = CD_MASK_ALL;
+
+  const int totpoint = tmp.totpoint = pointcloud_src->totpoint;
+  CustomData_copy(&pointcloud_src->pdata, &tmp.pdata, pmask, alloctype, totpoint);
+
+  BKE_pointcloud_update_customdata_pointers(&tmp);
+
+  CustomData_free(&pointcloud_dst->pdata, pointcloud_dst->totpoint);
+
+  /* skip the listbase */
+  MEMCPY_STRUCT_AFTER(pointcloud_dst, &tmp, id.prev);
+
+  if (take_ownership) {
+    if (alloctype == CD_ASSIGN) {
+      CustomData_free_typemask(&pointcloud_src->pdata, pointcloud_src->totpoint, ~pmask);
+    }
+    BKE_id_free(nullptr, pointcloud_src);
+  }
+}
+
+struct MinMaxResult {
+  float3 min;
+  float3 max;
+};
+
 static std::optional<blender::bounds::MinMaxResult<float3>> point_cloud_bounds(
     const PointCloud &pointcloud)
 {

source/blender/editors/include/UI_interface.h

@@ -2419,6 +2419,13 @@ void uiTemplateCacheFileLayers(uiLayout *layout,
                                const struct bContext *C,
                                struct PointerRNA *fileptr);
 
+/**
+ * Draw the attribute remapping related properties of the CacheFile.
+ */
+void uiTemplateCacheFileAttributeRemapping(uiLayout *layout,
+                                           const struct bContext *C,
+                                           struct PointerRNA *fileptr);
+
 /* Default UIList class name, keep in sync with its declaration in bl_ui/__init__.py */
 #define UI_UL_DEFAULT_CLASS_NAME "UI_UL_list"
 enum uiTemplateListFlags {

source/blender/editors/interface/interface_intern.h

@@ -1477,6 +1477,9 @@ void UI_OT_eyedropper_gpencil_color(struct wmOperatorType *ot);
 
 struct uiListType *UI_UL_asset_view(void);
 
+/* interface_templates.c */
+struct uiListType *UI_UL_cache_file_attribute_mappings(void);
+
 /**
  * For use with #ui_rna_collection_search_update_fn.
  */

source/blender/editors/interface/interface_template_list.cc

@@ -1309,6 +1309,7 @@ void ED_uilisttypes_ui()
 {
   WM_uilisttype_add(UI_UL_asset_view());
   WM_uilisttype_add(UI_UL_cache_file_layers());
+  WM_uilisttype_add(UI_UL_cache_file_attribute_mappings());
 }
 
 /** \} */

source/blender/editors/interface/interface_templates.c

@@ -6505,6 +6505,63 @@ bool uiTemplateCacheFilePointer(PointerRNA *ptr, const char *propname, PointerRN
   return true;
 }
 
+static void cache_file_attribute_mapping_item(uiList *UNUSED(ui_list),
+                                              bContext *UNUSED(C),
+                                              uiLayout *layout,
+                                              PointerRNA *UNUSED(dataptr),
+                                              PointerRNA *itemptr,
+                                              int UNUSED(icon),
+                                              PointerRNA *UNUSED(active_dataptr),
+                                              const char *UNUSED(active_propname),
+                                              int UNUSED(index),
+                                              int UNUSED(flt_flag))
+{
+  uiLayout *row = uiLayoutRow(layout, true);
+  uiItemR(row, itemptr, "name", UI_ITEM_R_NO_BG, "", ICON_NONE);
+  uiItemR(row, itemptr, "mapping", UI_ITEM_R_NO_BG, "", ICON_NONE);
+  uiItemR(row, itemptr, "domain", UI_ITEM_R_NO_BG, "", ICON_NONE);
+}
+
+uiListType *UI_UL_cache_file_attribute_mappings()
+{
+  uiListType *list_type = (uiListType *)MEM_callocN(sizeof(*list_type), __func__);
+
+  BLI_strncpy(list_type->idname, "UI_UL_cache_file_attribute_mappings", sizeof(list_type->idname));
+  list_type->draw_item = cache_file_attribute_mapping_item;
+
+  return list_type;
+}
+
+void uiTemplateCacheFileAttributeRemapping(uiLayout *layout,
+                                           const bContext *C,
+                                           PointerRNA *fileptr)
+{
+  /* Ensure that the context has a CacheFile as this may not be set inside of modifiers panels. */
+  uiLayoutSetContextPointer(layout, "edit_cachefile", fileptr);
+
+  uiLayout *row = uiLayoutRow(layout, false);
+  uiLayout *col = uiLayoutColumn(row, true);
+
+  uiTemplateList(col,
+                 (bContext *)C,
+                 "UI_UL_cache_file_attribute_mappings",
+                 "cache_file_attribute_mappings",
+                 fileptr,
+                 "attribute_mappings",
+                 fileptr,
+                 "active_attribute_mapping_index",
+                 "",
+                 1,
+                 5,
+                 UILST_LAYOUT_DEFAULT,
+                 1,
+                 UI_TEMPLATE_LIST_FLAG_NONE);
+
+  col = uiLayoutColumn(row, true);
+  uiItemO(col, "", ICON_ADD, "cachefile.attribute_mapping_add");
+  uiItemO(col, "", ICON_REMOVE, "cachefile.attribute_mapping_remove");
+}
+
 void uiTemplateCacheFile(uiLayout *layout,
                          const bContext *C,
                          PointerRNA *ptr,

source/blender/editors/io/io_cache.c

@@ -312,3 +312,78 @@ void CACHEFILE_OT_layer_move(wmOperatorType *ot)
                "Direction",
                "Direction to move the active vertex group towards");
 }
+
+/* ***************************** Add Attribute Mapping Operator **************************** */
+
+static bool cachefile_attribute_mapping_poll(bContext *C)
+{
+  return CTX_data_edit_cachefile(C) != NULL;
+}
+
+static int cachefile_attribute_mapping_add_exec(bContext *C, wmOperator *UNUSED(op))
+{
+  CacheFile *cache_file = CTX_data_edit_cachefile(C);
+
+  if (!cache_file) {
+    return OPERATOR_CANCELLED;
+  }
+
+  BKE_cachefile_add_attribute_mapping(
+      cache_file, NULL, CACHEFILE_ATTRIBUTE_MAP_NONE, CACHEFILE_ATTR_MAP_DOMAIN_AUTO);
+
+  /* Since the mapping is not initialized, adding a mapping does not trigger a CacheFile update. */
+
+  return OPERATOR_FINISHED;
+}
+
+void CACHEFILE_OT_attribute_mapping_add(wmOperatorType *ot)
+{
+  ot->name = "Add Attribute Mapping";
+  ot->description = "Add an attribute mapping for this CacheFile";
+  ot->idname = __func__;
+
+  /* api callbacks */
+  ot->exec = cachefile_attribute_mapping_add_exec;
+  ot->poll = cachefile_attribute_mapping_poll;
+
+  /* flags */
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+}
+
+/* ***************************** Remove Attribute Mapping Operator **************************** */
+
+static int cachefile_attribute_mapping_remove_exec(bContext *C, wmOperator *UNUSED(op))
+{
+  CacheFile *cache_file = CTX_data_edit_cachefile(C);
+
+  if (!cache_file) {
+    return OPERATOR_CANCELLED;
+  }
+
+  CacheAttributeMapping *mapping = BKE_cachefile_get_active_attribute_mapping(cache_file);
+
+  if (!mapping) {
+    return OPERATOR_CANCELLED;
+  }
+
+  BKE_cachefile_remove_attribute_mapping(cache_file, mapping);
+
+  Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
+  BKE_cachefile_reload(depsgraph, cache_file);
+
+  return OPERATOR_FINISHED;
+}
+
+void CACHEFILE_OT_attribute_mapping_remove(wmOperatorType *ot)
+{
+  ot->name = "Remove Attribute Mapping";
+  ot->description = "Remove an attribute mapping from this CacheFile";
+  ot->idname = __func__;
+
+  /* api callbacks */
+  ot->exec = cachefile_attribute_mapping_remove_exec;
+  ot->poll = cachefile_attribute_mapping_poll;
+
+  /* flags */
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+}

source/blender/editors/io/io_cache.h

@@ -15,3 +15,6 @@ void CACHEFILE_OT_reload(struct wmOperatorType *ot);
 void CACHEFILE_OT_layer_add(struct wmOperatorType *ot);
 void CACHEFILE_OT_layer_remove(struct wmOperatorType *ot);
 void CACHEFILE_OT_layer_move(struct wmOperatorType *ot);
+
+void CACHEFILE_OT_attribute_mapping_add(struct wmOperatorType *ot);
+void CACHEFILE_OT_attribute_mapping_remove(struct wmOperatorType *ot);

source/blender/editors/io/io_ops.c

@@ -58,5 +58,8 @@ void ED_operatortypes_io(void)
   WM_operatortype_append(CACHEFILE_OT_layer_remove);
   WM_operatortype_append(CACHEFILE_OT_layer_move);
 
+  WM_operatortype_append(CACHEFILE_OT_attribute_mapping_add);
+  WM_operatortype_append(CACHEFILE_OT_attribute_mapping_remove);
+
   WM_operatortype_append(WM_OT_obj_export);
 }

source/blender/io/alembic/ABC_alembic.h

@@ -14,6 +14,8 @@ extern "C" {
 struct CacheArchiveHandle;
 struct CacheFileLayer;
 struct CacheReader;
+struct Curves;
+struct GeometrySet;
 struct ListBase;
 struct Main;
 struct Mesh;
@@ -99,15 +101,23 @@ void ABC_get_transform(struct CacheReader *reader,
                        float time,
                        float scale);
 
-/* Either modifies existing_mesh in-place or constructs a new mesh. */
-struct Mesh *ABC_read_mesh(struct CacheReader *reader,
-                           struct Object *ob,
-                           struct Mesh *existing_mesh,
-                           float time,
-                           const char **err_str,
-                           int read_flags,
-                           const char *velocity_name,
-                           float velocity_scale);
+typedef struct ABCReadParams {
+  float time;
+  int read_flags;
+  const char *velocity_name;
+  float velocity_scale;
+
+  ListBase *mappings;
+} ABCReadParams;
+
+#ifdef __cplusplus
+/* Either modifies the existing geometry component, or create a new one. */
+void ABC_read_geometry(CacheReader *reader,
+                       Object *ob,
+                       GeometrySet &geometry_set,
+                       const ABCReadParams *params,
+                       const char **err_str);
+#endif
 
 bool ABC_mesh_topology_changed(struct CacheReader *reader,
                                struct Object *ob,

source/blender/io/alembic/CMakeLists.txt

@@ -7,9 +7,11 @@ set(INC
   ../../blenkernel
   ../../blenlib
   ../../blenloader
+  ../../blentranslation
   ../../bmesh
   ../../depsgraph
   ../../editors/include
+  ../../functions
   ../../makesdna
   ../../makesrna
   ../../windowmanager
@@ -30,6 +32,8 @@ set(SRC
   intern/abc_reader_archive.cc
   intern/abc_reader_camera.cc
   intern/abc_reader_curves.cc
+  intern/abc_reader_instance.cc
+  intern/abc_reader_manager.cc
   intern/abc_reader_mesh.cc
   intern/abc_reader_nurbs.cc
   intern/abc_reader_object.cc
@@ -60,6 +64,8 @@ set(SRC
   intern/abc_reader_archive.h
   intern/abc_reader_camera.h
   intern/abc_reader_curves.h
+  intern/abc_reader_instance.h
+  intern/abc_reader_manager.h
   intern/abc_reader_mesh.h
   intern/abc_reader_nurbs.h
   intern/abc_reader_object.h

source/blender/io/alembic/exporter/abc_writer_mesh.cc

@@ -76,6 +76,12 @@ static void get_loop_normals(struct Mesh *mesh,
 ABCGenericMeshWriter::ABCGenericMeshWriter(const ABCWriterConstructorArgs &args)
     : ABCAbstractWriter(args), is_subd_(false)
 {
+  attribute_exporter_ = nullptr;
+}
+
+ABCGenericMeshWriter::~ABCGenericMeshWriter()
+{
+  delete_attribute_exporter(attribute_exporter_);
 }
 
 void ABCGenericMeshWriter::create_alembic_objects(const HierarchyContext *context)
@@ -254,10 +260,6 @@ void ABCGenericMeshWriter::write_mesh(HierarchyContext &context, Mesh *mesh)
     mesh_sample.setNormals(normals_sample);
   }
 
-  if (args_.export_params->orcos) {
-    write_generated_coordinates(abc_poly_mesh_schema_.getArbGeomParams(), m_custom_data_config);
-  }
-
   if (get_velocities(mesh, velocities)) {
     mesh_sample.setVelocities(V3fArraySample(velocities));
   }
@@ -266,7 +268,6 @@ void ABCGenericMeshWriter::write_mesh(HierarchyContext &context, Mesh *mesh)
   mesh_sample.setSelfBounds(bounding_box_);
 
   abc_poly_mesh_schema_.set(mesh_sample);
-
   write_arb_geo_params(mesh);
 }
 
@@ -308,10 +309,6 @@ void ABCGenericMeshWriter::write_subd(HierarchyContext &context, struct Mesh *me
         abc_subdiv_schema_.getArbGeomParams(), m_custom_data_config, &mesh->ldata, CD_MLOOPUV);
   }
 
-  if (args_.export_params->orcos) {
-    write_generated_coordinates(abc_subdiv_schema_.getArbGeomParams(), m_custom_data_config);
-  }
-
   if (!edge_crease_indices.empty()) {
     subdiv_sample.setCreaseIndices(Int32ArraySample(edge_crease_indices));
     subdiv_sample.setCreaseLengths(Int32ArraySample(edge_crease_lengths));
@@ -347,8 +344,15 @@ void ABCGenericMeshWriter::write_face_sets(Object *object, struct Mesh *mesh, Sc
 
 void ABCGenericMeshWriter::write_arb_geo_params(struct Mesh *me)
 {
+  int64_t cd_mask = CD_MASK_ALL;
   if (!args_.export_params->vcolors) {
-    return;
+    cd_mask &= ~CD_MASK_MCOL;
+  }
+  if (!args_.export_params->uvs) {
+    cd_mask &= ~CD_MASK_MLOOPUV;
+  }
+  if (!args_.export_params->orcos) {
+    cd_mask &= ~CD_MASK_ORCO;
   }
 
   OCompoundProperty arb_geom_params;
@@ -358,7 +362,13 @@ void ABCGenericMeshWriter::write_arb_geo_params(struct Mesh *me)
   else {
     arb_geom_params = abc_poly_mesh_.getSchema().getArbGeomParams();
   }
-  write_custom_data(arb_geom_params, m_custom_data_config, &me->ldata, CD_MLOOPCOL);
+
+  if (!attribute_exporter_) {
+    attribute_exporter_ = make_attribute_exporter(&me->id, cd_mask, arb_geom_params);
+  }
+
+  set_timesample_index(attribute_exporter_, m_custom_data_config.timesample_index);
+  attribute_exporter_->export_attributes();
 }
 
 bool ABCGenericMeshWriter::get_velocities(struct Mesh *mesh, std::vector<Imath::V3f> &vels)

source/blender/io/alembic/exporter/abc_writer_mesh.h

@@ -34,9 +34,13 @@ class ABCGenericMeshWriter : public ABCAbstractWriter {
 
   CDStreamConfig m_custom_data_config;
 
+  GenericAttributeExporter *attribute_exporter_;
+
  public:
   explicit ABCGenericMeshWriter(const ABCWriterConstructorArgs &args);
 
+  ~ABCGenericMeshWriter();
+
   virtual void create_alembic_objects(const HierarchyContext *context) override;
   virtual Alembic::Abc::OObject get_alembic_object() const override;
   Alembic::Abc::OCompoundProperty abc_prop_for_custom_props() override;

source/blender/io/alembic/intern/abc_customdata.h

@@ -11,17 +11,29 @@
 
 #include <map>
 
+#include "BKE_attribute.h"
+
+#include "BLI_color.hh"
+#include "BLI_listbase_wrapper.hh"
+#include "BLI_math_vec_types.hh"
+#include "BLI_span.hh"
+
+struct CacheAttributeMapping;
 struct CustomData;
+struct ID;
 struct MLoop;
 struct MLoopUV;
 struct MPoly;
 struct MVert;
 struct Mesh;
+struct MCol;
 
 using Alembic::Abc::ICompoundProperty;
 using Alembic::Abc::OCompoundProperty;
 namespace blender::io::alembic {
 
+class AttributeSelector;
+
 struct UVSample {
   std::vector<Imath::V2f> uvs;
   std::vector<uint32_t> indices;
@@ -43,10 +55,12 @@ struct CDStreamConfig {
 
   bool pack_uvs;
 
-  /* TODO(kevin): might need a better way to handle adding and/or updating
-   * custom data such that it updates the custom data holder and its pointers properly. */
+  /* NOTE: the mesh is mostly used for iterating over loops for loop attributes (UVs, MCol, etc.).
+   * It would be nice to remove it, in favor of a more generic way to iterate valid attribute
+   * indices.
+   */
   Mesh *mesh;
-  void *(*add_customdata_cb)(Mesh *mesh, const char *name, int data_type);
+  ID *id;
 
   float weight;
   float time;
@@ -57,6 +71,13 @@ struct CDStreamConfig {
 
   const char **modifier_error_message;
 
+  DomainInfo domain_info[ATTR_DOMAIN_NUM];
+
+  /* For error reporting when reading vertex colors. */
+  std::string iobject_full_name;
+
+  const AttributeSelector *attr_selector;
+
   /* Alembic needs Blender to keep references to C++ objects (the destructors finalize the writing
    * to ABC). The following fields are all used to keep these references. */
 
@@ -78,12 +99,12 @@ struct CDStreamConfig {
         totvert(0),
         pack_uvs(false),
         mesh(NULL),
-        add_customdata_cb(NULL),
         weight(0.0f),
         time(0.0f),
         index(0),
         ceil_index(0),
-        modifier_error_message(NULL)
+        modifier_error_message(NULL),
+        attr_selector(nullptr)
   {
   }
 };
@@ -94,38 +115,126 @@ struct CDStreamConfig {
  * For now the active layer is used, maybe needs a better way to choose this. */
 const char *get_uv_sample(UVSample &sample, const CDStreamConfig &config, CustomData *data);
 
-void write_generated_coordinates(const OCompoundProperty &prop, CDStreamConfig &config);
-
-void read_generated_coordinates(const ICompoundProperty &prop,
-                                const CDStreamConfig &config,
-                                const Alembic::Abc::ISampleSelector &iss);
-
 void write_custom_data(const OCompoundProperty &prop,
                        CDStreamConfig &config,
                        CustomData *data,
                        int data_type);
 
-void read_custom_data(const std::string &iobject_full_name,
-                      const ICompoundProperty &prop,
-                      const CDStreamConfig &config,
-                      const Alembic::Abc::ISampleSelector &iss);
-
-typedef enum {
-  ABC_UV_SCOPE_NONE,
-  ABC_UV_SCOPE_LOOP,
-  ABC_UV_SCOPE_VERTEX,
-} AbcUvScope;
-
-/**
- * UVs can be defined per-loop (one value per vertex per face), or per-vertex (one value per
- * vertex). The first case is the most common, as this is the standard way of storing this data
- * given that some vertices might be on UV seams and have multiple possible UV coordinates; the
- * second case can happen when the mesh is split according to the UV islands, in which case storing
- * a single UV value per vertex allows to de-duplicate data and thus to reduce the file size since
- * vertices are guaranteed to only have a single UV coordinate.
+/* Need special handling for:
+ * - creases (vertex/edge)
+ * - velocity
+ * - generated coordinate
+ * - UVs
+ * - vertex colors
  */
-AbcUvScope get_uv_scope(const Alembic::AbcGeom::GeometryScope scope,
-                        const CDStreamConfig &config,
-                        const Alembic::AbcGeom::UInt32ArraySamplePtr &indices);
+class GenericAttributeExporter {
+  ID *m_id;
+  int64_t cd_mask = CD_MASK_ALL;
+
+ public:
+  GenericAttributeExporter(ID *id, int64_t cd_mask_) : m_id(id), cd_mask(cd_mask_)
+  {
+  }
+
+  void export_attributes();
+
+ protected:
+  virtual void export_attribute(blender::Span<bool> span,
+                                const std::string &name,
+                                AttributeDomain domain) = 0;
+
+  virtual void export_attribute(blender::Span<char> span,
+                                const std::string &name,
+                                AttributeDomain domain) = 0;
+
+  virtual void export_attribute(blender::Span<int> span,
+                                const std::string &name,
+                                AttributeDomain domain) = 0;
+
+  virtual void export_attribute(blender::Span<float> span,
+                                const std::string &name,
+                                AttributeDomain domain) = 0;
+
+  virtual void export_attribute(blender::Span<float2> span,
+                                const std::string &name,
+                                AttributeDomain domain) = 0;
+
+  virtual void export_attribute(blender::Span<float3> span,
+                                const std::string &name,
+                                AttributeDomain domain) = 0;
+
+  virtual void export_attribute(blender::Span<ColorGeometry4f> span,
+                                const std::string &name,
+                                AttributeDomain domain) = 0;
+
+  virtual void export_attribute(blender::Span<MLoopUV> span,
+                                const std::string &name,
+                                AttributeDomain domain) = 0;
+
+  virtual void export_attribute(blender::Span<MCol> span,
+                                const std::string &name,
+                                AttributeDomain domain) = 0;
+
+  template<typename BlenderDataType>
+  void export_customdata_layer(CustomDataLayer *layer, DomainInfo info, AttributeDomain domain)
+  {
+    BlenderDataType *data = static_cast<BlenderDataType *>(layer->data);
+    int64_t size = static_cast<int64_t>(info.length);
+    blender::Span<BlenderDataType> data_span(data, size);
+    this->export_attribute(data_span, layer->name, domain);
+  }
+
+  void export_generated_coordinates(CustomDataLayer *layer,
+                                    DomainInfo info,
+                                    AttributeDomain domain);
+
+  void export_attribute_for_domain(DomainInfo info, AttributeDomain domain);
+};
+
+GenericAttributeExporter *make_attribute_exporter(ID *id,
+                                                  int64_t cd_mask,
+                                                  OCompoundProperty &prop);
+
+void set_timesample_index(GenericAttributeExporter *exporter, int timesample_index);
+
+void delete_attribute_exporter(GenericAttributeExporter *exporter);
+
+class AttributeSelector {
+  /* Name of the velocity attribute, it is ignored since we deal with separately. */
+  std::string velocity_attribute = "";
+
+  int read_flags = 0;
+
+  ListBaseWrapper<const CacheAttributeMapping> mappings;
+
+ public:
+  AttributeSelector(ListBase *mappings_) : mappings(mappings_)
+  {
+  }
+
+  void set_velocity_attribute(const char *name);
+
+  void set_read_flags(int flags);
+
+  const CacheAttributeMapping *get_mapping(const std::string &attr_name) const;
+
+  const std::string &velocity_name() const;
+
+  bool uvs_requested() const;
+
+  bool vertex_colors_requested() const;
+
+  bool original_coordinates_requested() const;
+
+  bool select_attribute(const std::string &attr_name) const;
+};
+
+void read_arbitrary_attributes(const CDStreamConfig &config,
+                               const ICompoundProperty &schema,
+                               const Alembic::AbcGeom::IV2fGeomParam &primary_uvs,
+                               const Alembic::Abc::ISampleSelector &sample_sel,
+                               float velocity_scale);
+
+bool has_animated_attributes(const ICompoundProperty &arb_geom_params);
 
 }  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_camera.cc

@@ -59,7 +59,9 @@ bool AbcCameraReader::accepts_object_type(
   return true;
 }
 
-void AbcCameraReader::readObjectData(Main *bmain, const ISampleSelector &sample_sel)
+void AbcCameraReader::readObjectData(Main *bmain,
+                                     const AbcReaderManager & /*manager*/,
+                                     const ISampleSelector &sample_sel)
 {
   Camera *bcam = static_cast<Camera *>(BKE_camera_add(bmain, m_data_name.c_str()));
 

source/blender/io/alembic/intern/abc_reader_camera.h

@@ -20,7 +20,9 @@ class AbcCameraReader final : public AbcObjectReader {
                            const Object *const ob,
                            const char **err_str) const override;
 
-  void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel) override;
+  void readObjectData(Main *bmain,
+                      const AbcReaderManager &manager,
+                      const Alembic::Abc::ISampleSelector &sample_sel) override;
 };
 
 }  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_curves.cc

@@ -7,6 +7,7 @@
 
 #include "abc_reader_curves.h"
 #include "abc_axis_conversion.h"
+#include "abc_customdata.h"
 #include "abc_reader_transform.h"
 #include "abc_util.h"
 
@@ -14,14 +15,17 @@
 
 #include "MEM_guardedalloc.h"
 
-#include "DNA_curve_types.h"
+#include "DNA_curves_types.h"
 #include "DNA_object_types.h"
 
 #include "BLI_listbase.h"
 
-#include "BKE_curve.h"
+#include "BKE_curves.h"
+#include "BKE_curves.hh"
+#include "BKE_geometry_set.hh"
 #include "BKE_mesh.h"
 #include "BKE_object.h"
+#include "BKE_spline.hh"
 
 using Alembic::Abc::FloatArraySamplePtr;
 using Alembic::Abc::Int32ArraySamplePtr;
@@ -66,7 +70,7 @@ bool AbcCurveReader::accepts_object_type(
     return false;
   }
 
-  if (ob->type != OB_CURVES_LEGACY) {
+  if (ob->type != OB_CURVES) {
     *err_str = "Object type mismatch, Alembic object path points to Curves.";
     return false;
   }
@@ -74,36 +78,234 @@ bool AbcCurveReader::accepts_object_type(
   return true;
 }
 
-void AbcCurveReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel)
+void AbcCurveReader::readObjectData(Main *bmain,
+                                    const AbcReaderManager & /*manager*/,
+                                    const Alembic::Abc::ISampleSelector &sample_sel)
 {
-  Curve *cu = BKE_curve_add(bmain, m_data_name.c_str(), OB_CURVES_LEGACY);
+  Curves *curves = static_cast<Curves *>(BKE_curves_add(bmain, m_data_name.c_str()));
 
-  cu->flag |= CU_3D;
-  cu->actvert = CU_ACT_NONE;
-  cu->resolu = 1;
+  m_object = BKE_object_add_only_object(bmain, OB_CURVES, m_object_name.c_str());
+  m_object->data = curves;
 
-  ICompoundProperty user_props = m_curves_schema.getUserProperties();
-  if (user_props) {
-    const PropertyHeader *header = user_props.getPropertyHeader(ABC_CURVE_RESOLUTION_U_PROPNAME);
-    if (header != nullptr && header->isScalar() && IInt16Property::matches(*header)) {
-      IInt16Property resolu(user_props, header->getName());
-      cu->resolu = resolu.getValue(sample_sel);
-    }
-  }
-
-  m_object = BKE_object_add_only_object(bmain, OB_CURVES_LEGACY, m_object_name.c_str());
-  m_object->data = cu;
-
-  read_curve_sample(cu, m_curves_schema, sample_sel);
+  read_curves_sample(curves, m_curves_schema, sample_sel);
 
   if (m_settings->always_add_cache_reader || has_animations(m_curves_schema, m_settings)) {
     addCacheModifier();
   }
 }
 
-void AbcCurveReader::read_curve_sample(Curve *cu,
-                                       const ICurvesSchema &schema,
-                                       const ISampleSelector &sample_sel)
+static short get_curve_resolution(const ICurvesSchema &schema,
+                                  const Alembic::Abc::ISampleSelector &sample_sel)
+{
+  ICompoundProperty user_props = schema.getUserProperties();
+  if (user_props) {
+    const PropertyHeader *header = user_props.getPropertyHeader(ABC_CURVE_RESOLUTION_U_PROPNAME);
+    if (header != nullptr && header->isScalar() && IInt16Property::matches(*header)) {
+      IInt16Property resolu(user_props, header->getName());
+      return resolu.getValue(sample_sel);
+    }
+  }
+
+  return 1;
+}
+
+static short get_curve_order(Alembic::AbcGeom::CurveType abc_curve_type,
+                             const UcharArraySamplePtr orders,
+                             size_t curve_index)
+{
+  switch (abc_curve_type) {
+    case Alembic::AbcGeom::kCubic:
+      return 4;
+    case Alembic::AbcGeom::kVariableOrder:
+      if (orders && orders->size() > curve_index) {
+        return static_cast<short>((*orders)[curve_index]);
+      }
+      ATTR_FALLTHROUGH;
+    case Alembic::AbcGeom::kLinear:
+    default:
+      return 2;
+  }
+}
+
+static int get_curve_overlap(Alembic::AbcGeom::CurvePeriodicity periodicity,
+                             const P3fArraySamplePtr positions,
+                             int idx,
+                             int num_verts,
+                             short order)
+{
+  if (periodicity == Alembic::AbcGeom::kPeriodic) {
+    /* Check the number of points which overlap, we don't have
+     * overlapping points in Blender, but other software do use them to
+     * indicate that a curve is actually cyclic. Usually the number of
+     * overlapping points is equal to the order/degree of the curve.
+     */
+
+    const int start = idx;
+    const int end = idx + num_verts;
+    int overlap = 0;
+
+    for (int j = start, k = end - order; j < order; j++, k++) {
+      const Imath::V3f &p1 = (*positions)[j];
+      const Imath::V3f &p2 = (*positions)[k];
+
+      if (p1 != p2) {
+        break;
+      }
+
+      overlap++;
+    }
+
+    /* TODO: Special case, need to figure out how it coincides with knots. */
+    if (overlap == 0 && num_verts > 2 && (*positions)[start] == (*positions)[end - 1]) {
+      overlap = 1;
+    }
+
+    /* There is no real cycles. */
+    return overlap;
+  }
+
+  /* kNonPeriodic is always assumed to have no overlap. */
+  return 0;
+}
+
+static int abc_curves_get_total_point_size(const Int32ArraySamplePtr num_vertices)
+{
+  if (!num_vertices) {
+    return 0;
+  }
+
+  int result = 0;
+  for (size_t i = 0; i < num_vertices->size(); i++) {
+    result += (*num_vertices)[i];
+  }
+  return result;
+}
+
+static void read_curves_sample_ex(Curves *curves,
+                                  const ICurvesSchema &schema,
+                                  const ICurvesSchema::Sample &smp,
+                                  const ISampleSelector sample_sel,
+                                  const AttributeSelector *attribute_selector,
+                                  const float velocity_scale,
+                                  const char **err_str)
+{
+  bke::CurvesGeometry &geometry = bke::CurvesGeometry::wrap(curves->geometry);
+  MutableSpan<int> offsets = geometry.offsets();
+  MutableSpan<float3> positions_ = geometry.positions();
+  MutableSpan<bool> cyclic = geometry.cyclic();
+
+  float *curves_weights = nullptr;
+  int *curves_orders = nullptr;
+
+  int *curves_resolution = static_cast<int *>(CustomData_add_layer_named(&geometry.curve_data,
+                                                                         CD_PROP_INT32,
+                                                                         CD_DEFAULT,
+                                                                         nullptr,
+                                                                         geometry.curve_size,
+                                                                         "resolution"));
+
+  const int resolution = get_curve_resolution(schema, sample_sel);
+  for (int64_t i : geometry.curves_range()) {
+    curves_resolution[i] = resolution;
+  }
+
+  if (!geometry.radius) {
+    geometry.radius = static_cast<float *>(CustomData_add_layer_named(
+        &geometry.point_data, CD_PROP_FLOAT, CD_DEFAULT, nullptr, geometry.point_size, "radius"));
+  }
+
+  /* Knots are not imported anymore. */
+  const Int32ArraySamplePtr num_vertices = smp.getCurvesNumVertices();
+  const P3fArraySamplePtr positions = smp.getPositions();
+  const FloatArraySamplePtr weights = smp.getPositionWeights();
+  const CurvePeriodicity periodicity = smp.getWrap();
+  const UcharArraySamplePtr orders = smp.getOrders();
+
+  const IFloatGeomParam widths_param = schema.getWidthsParam();
+  FloatArraySamplePtr radiuses;
+
+  if (widths_param.valid()) {
+    IFloatGeomParam::Sample wsample = widths_param.getExpandedValue(sample_sel);
+    radiuses = wsample.getVals();
+  }
+
+  const bool do_radius = (radiuses != nullptr) && (radiuses->size() > 1);
+  float radius = (radiuses && radiuses->size() == 1) ? (*radiuses)[0] : 1.0f;
+
+  const bool do_weights = (weights != nullptr) && (weights->size() > 1);
+  if (do_weights) {
+    curves_weights = static_cast<float *>(CustomData_add_layer_named(&geometry.point_data,
+                                                                     CD_PROP_FLOAT,
+                                                                     CD_DEFAULT,
+                                                                     nullptr,
+                                                                     geometry.point_size,
+                                                                     "nurbs_weight"));
+  }
+
+  const bool do_curves_orders = (orders != nullptr) && (orders->size() > 1);
+  if (do_curves_orders) {
+    curves_orders = static_cast<int *>(CustomData_add_layer_named(&geometry.curve_data,
+                                                                  CD_PROP_INT32,
+                                                                  CD_DEFAULT,
+                                                                  nullptr,
+                                                                  geometry.curve_size,
+                                                                  "nurbs_order"));
+  }
+
+  int offset = 0;
+  size_t position_offset = 0;
+  for (size_t i = 0; i < num_vertices->size(); i++) {
+    const int num_verts = (*num_vertices)[i];
+    offsets[i] = offset;
+
+    const int curve_order = get_curve_order(smp.getType(), orders, i);
+    if (do_curves_orders) {
+      curves_orders[i] = curve_order;
+    }
+
+    /* Check if the curve is cyclic. */
+    const int overlap = get_curve_overlap(
+        periodicity, positions, position_offset, num_verts, curve_order);
+
+    const bool is_cyclic = overlap != 0;
+    cyclic[i] = is_cyclic;
+
+    for (int j = 0; j < num_verts - overlap; j++, position_offset++) {
+      const Imath::V3f &pos = (*positions)[position_offset];
+
+      copy_zup_from_yup(positions_[position_offset], pos.getValue());
+
+      if (do_radius) {
+        radius = (*radiuses)[position_offset];
+      }
+      geometry.radius[position_offset] = radius;
+
+      if (do_weights) {
+        curves_weights[position_offset] = (*weights)[position_offset];
+      }
+    }
+
+    offset += num_verts;
+    /* Skip duplicate positions due to cyclicity. */
+    position_offset += overlap;
+  }
+
+  offsets[geometry.curve_size] = offset;
+
+  /* Attributes. */
+  CDStreamConfig config;
+  config.id = &curves->id;
+  config.attr_selector = attribute_selector;
+  config.time = sample_sel.getRequestedTime();
+  config.modifier_error_message = err_str;
+  BKE_id_attribute_get_domains(config.id, config.domain_info);
+
+  read_arbitrary_attributes(config, schema, {}, sample_sel, velocity_scale);
+}
+
+void AbcCurveReader::read_curves_sample(Curves *curves,
+                                        const ICurvesSchema &schema,
+                                        const ISampleSelector &sample_sel)
 {
   ICurvesSchema::Sample smp;
   try {
@@ -120,150 +322,22 @@ void AbcCurveReader::read_curve_sample(Curve *cu,
 
   const Int32ArraySamplePtr num_vertices = smp.getCurvesNumVertices();
   const P3fArraySamplePtr positions = smp.getPositions();
-  const FloatArraySamplePtr weights = smp.getPositionWeights();
-  const FloatArraySamplePtr knots = smp.getKnots();
-  const CurvePeriodicity periodicity = smp.getWrap();
-  const UcharArraySamplePtr orders = smp.getOrders();
 
-  const IFloatGeomParam widths_param = schema.getWidthsParam();
-  FloatArraySamplePtr radiuses;
+  const int point_size = abc_curves_get_total_point_size(num_vertices);
+  const int curve_size = static_cast<int>(num_vertices->size());
 
-  if (widths_param.valid()) {
-    IFloatGeomParam::Sample wsample = widths_param.getExpandedValue(sample_sel);
-    radiuses = wsample.getVals();
-  }
+  bke::CurvesGeometry &geometry = bke::CurvesGeometry::wrap(curves->geometry);
+  geometry.resize(point_size, curve_size);
 
-  int knot_offset = 0;
-
-  size_t idx = 0;
-  for (size_t i = 0; i < num_vertices->size(); i++) {
-    const int num_verts = (*num_vertices)[i];
-
-    Nurb *nu = static_cast<Nurb *>(MEM_callocN(sizeof(Nurb), "abc_getnurb"));
-    nu->resolu = cu->resolu;
-    nu->resolv = cu->resolv;
-    nu->pntsu = num_verts;
-    nu->pntsv = 1;
-    nu->flag |= CU_SMOOTH;
-
-    switch (smp.getType()) {
-      case Alembic::AbcGeom::kCubic:
-        nu->orderu = 4;
-        break;
-      case Alembic::AbcGeom::kVariableOrder:
-        if (orders && orders->size() > i) {
-          nu->orderu = static_cast<short>((*orders)[i]);
-          break;
-        }
-        ATTR_FALLTHROUGH;
-      case Alembic::AbcGeom::kLinear:
-      default:
-        nu->orderu = 2;
-    }
-
-    if (periodicity == Alembic::AbcGeom::kNonPeriodic) {
-      nu->flagu |= CU_NURB_ENDPOINT;
-    }
-    else if (periodicity == Alembic::AbcGeom::kPeriodic) {
-      nu->flagu |= CU_NURB_CYCLIC;
-
-      /* Check the number of points which overlap, we don't have
-       * overlapping points in Blender, but other software do use them to
-       * indicate that a curve is actually cyclic. Usually the number of
-       * overlapping points is equal to the order/degree of the curve.
-       */
-
-      const int start = idx;
-      const int end = idx + num_verts;
-      int overlap = 0;
-
-      for (int j = start, k = end - nu->orderu; j < nu->orderu; j++, k++) {
-        const Imath::V3f &p1 = (*positions)[j];
-        const Imath::V3f &p2 = (*positions)[k];
-
-        if (p1 != p2) {
-          break;
-        }
-
-        overlap++;
-      }
-
-      /* TODO: Special case, need to figure out how it coincides with knots. */
-      if (overlap == 0 && num_verts > 2 && (*positions)[start] == (*positions)[end - 1]) {
-        overlap = 1;
-      }
-
-      /* There is no real cycles. */
-      if (overlap == 0) {
-        nu->flagu &= ~CU_NURB_CYCLIC;
-        nu->flagu |= CU_NURB_ENDPOINT;
-      }
-
-      nu->pntsu -= overlap;
-    }
-
-    const bool do_weights = (weights != nullptr) && (weights->size() > 1);
-    float weight = 1.0f;
-
-    const bool do_radius = (radiuses != nullptr) && (radiuses->size() > 1);
-    float radius = (radiuses && radiuses->size() == 1) ? (*radiuses)[0] : 1.0f;
-
-    nu->type = CU_NURBS;
-
-    nu->bp = static_cast<BPoint *>(MEM_callocN(sizeof(BPoint) * nu->pntsu, "abc_getnurb"));
-    BPoint *bp = nu->bp;
-
-    for (int j = 0; j < nu->pntsu; j++, bp++, idx++) {
-      const Imath::V3f &pos = (*positions)[idx];
-
-      if (do_radius) {
-        radius = (*radiuses)[idx];
-      }
-
-      if (do_weights) {
-        weight = (*weights)[idx];
-      }
-
-      copy_zup_from_yup(bp->vec, pos.getValue());
-      bp->vec[3] = weight;
-      bp->f1 = SELECT;
-      bp->radius = radius;
-      bp->weight = 1.0f;
-    }
-
-    if (knots && knots->size() != 0) {
-      nu->knotsu = static_cast<float *>(
-          MEM_callocN(KNOTSU(nu) * sizeof(float), "abc_setsplineknotsu"));
-
-      /* TODO: second check is temporary, for until the check for cycles is rock solid. */
-      if (periodicity == Alembic::AbcGeom::kPeriodic && (KNOTSU(nu) == knots->size() - 2)) {
-        /* Skip first and last knots. */
-        for (size_t i = 1; i < knots->size() - 1; i++) {
-          nu->knotsu[i - 1] = (*knots)[knot_offset + i];
-        }
-      }
-      else {
-        /* TODO: figure out how to use the knots array from other
-         * software in this case. */
-        BKE_nurb_knot_calc_u(nu);
-      }
-
-      knot_offset += knots->size();
-    }
-    else {
-      BKE_nurb_knot_calc_u(nu);
-    }
-
-    BLI_addtail(BKE_curve_nurbs_get(cu), nu);
-  }
+  read_curves_sample_ex(curves, m_curves_schema, smp, sample_sel, nullptr, 0.0f, nullptr);
 }
 
-Mesh *AbcCurveReader::read_mesh(Mesh *existing_mesh,
-                                const ISampleSelector &sample_sel,
-                                int /*read_flag*/,
-                                const char * /*velocity_name*/,
-                                const float /*velocity_scale*/,
-                                const char **err_str)
+void AbcCurveReader::read_geometry(GeometrySet &geometry_set,
+                                   const Alembic::Abc::ISampleSelector &sample_sel,
+                                   const AttributeSelector *attribute_selector,
+                                   int /*read_flag*/,
+                                   const float velocity_scale,
+                                   const char **err_str)
 {
   ICurvesSchema::Sample sample;
 
@@ -277,61 +351,22 @@ Mesh *AbcCurveReader::read_mesh(Mesh *existing_mesh,
            m_curves_schema.getName().c_str(),
            sample_sel.getRequestedTime(),
            ex.what());
-    return existing_mesh;
+    return;
   }
 
-  const P3fArraySamplePtr &positions = sample.getPositions();
   const Int32ArraySamplePtr num_vertices = sample.getCurvesNumVertices();
+  const P3fArraySamplePtr positions = sample.getPositions();
 
-  int vertex_idx = 0;
-  int curve_idx;
-  Curve *curve = static_cast<Curve *>(m_object->data);
+  Curves *curves = geometry_set.get_curves_for_write();
 
-  const int curve_count = BLI_listbase_count(&curve->nurb);
-  bool same_topology = curve_count == num_vertices->size();
+  const int point_size = abc_curves_get_total_point_size(num_vertices);
+  const int curve_size = static_cast<int>(num_vertices->size());
 
-  if (same_topology) {
-    Nurb *nurbs = static_cast<Nurb *>(curve->nurb.first);
-    for (curve_idx = 0; nurbs; nurbs = nurbs->next, curve_idx++) {
-      const int num_in_alembic = (*num_vertices)[curve_idx];
-      const int num_in_blender = nurbs->pntsu;
+  bke::CurvesGeometry &geometry = bke::CurvesGeometry::wrap(curves->geometry);
+  geometry.resize(point_size, curve_size);
 
-      if (num_in_alembic != num_in_blender) {
-        same_topology = false;
-        break;
-      }
-    }
-  }
-
-  if (!same_topology) {
-    BKE_nurbList_free(&curve->nurb);
-    read_curve_sample(curve, m_curves_schema, sample_sel);
-  }
-  else {
-    Nurb *nurbs = static_cast<Nurb *>(curve->nurb.first);
-    for (curve_idx = 0; nurbs; nurbs = nurbs->next, curve_idx++) {
-      const int totpoint = (*num_vertices)[curve_idx];
-
-      if (nurbs->bp) {
-        BPoint *point = nurbs->bp;
-
-        for (int i = 0; i < totpoint; i++, point++, vertex_idx++) {
-          const Imath::V3f &pos = (*positions)[vertex_idx];
-          copy_zup_from_yup(point->vec, pos.getValue());
-        }
-      }
-      else if (nurbs->bezt) {
-        BezTriple *bezier = nurbs->bezt;
-
-        for (int i = 0; i < totpoint; i++, bezier++, vertex_idx++) {
-          const Imath::V3f &pos = (*positions)[vertex_idx];
-          copy_zup_from_yup(bezier->vec[1], pos.getValue());
-        }
-      }
-    }
-  }
-
-  return BKE_mesh_new_nomain_from_curve(m_object);
+  read_curves_sample_ex(
+      curves, m_curves_schema, sample, sample_sel, attribute_selector, velocity_scale, err_str);
 }
 
 }  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_curves.h

@@ -9,7 +9,7 @@
 #include "abc_reader_mesh.h"
 #include "abc_reader_object.h"
 
-struct Curve;
+struct Curves;
 
 #define ABC_CURVE_RESOLUTION_U_PROPNAME "blender:resolution"
 
@@ -26,7 +26,10 @@ class AbcCurveReader final : public AbcObjectReader {
                            const Object *const ob,
                            const char **err_str) const override;
 
-  void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel) override;
+  void readObjectData(Main *bmain,
+                      const AbcReaderManager &manager,
+                      const Alembic::Abc::ISampleSelector &sample_sel) override;
+
   /**
    * \note Alembic only stores data about control points, but the Mesh
    * passed from the cache modifier contains the #DispList, which has more data
@@ -34,16 +37,16 @@ class AbcCurveReader final : public AbcObjectReader {
    * object directly and create a new Mesh from that. Also we might need to
    * create new or delete existing NURBS in the curve.
    */
-  struct Mesh *read_mesh(struct Mesh *existing_mesh,
-                         const Alembic::Abc::ISampleSelector &sample_sel,
-                         int read_flag,
-                         const char *velocity_name,
-                         float velocity_scale,
-                         const char **err_str) override;
+  void read_geometry(GeometrySet &geometry_set,
+                     const Alembic::Abc::ISampleSelector &sample_sel,
+                     const AttributeSelector *attribute_selector,
+                     int read_flag,
+                     const float velocity_scale,
+                     const char **err_str) override;
 
-  void read_curve_sample(Curve *cu,
-                         const Alembic::AbcGeom::ICurvesSchema &schema,
-                         const Alembic::Abc::ISampleSelector &sample_selector);
+  void read_curves_sample(Curves *curves,
+                          const Alembic::AbcGeom::ICurvesSchema &schema,
+                          const Alembic::Abc::ISampleSelector &sample_selector);
 };
 
 }  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_instance.cc

@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "abc_reader_instance.h"
+
+#include "DNA_object_types.h"
+
+#include "BLI_assert.h"
+
+#include "BKE_lib_id.h"
+#include "BKE_lib_remap.h"
+#include "BKE_object.h"
+
+#include "abc_reader_manager.h"
+
+namespace blender::io::alembic {
+
+AbcInstanceReader::AbcInstanceReader(const Alembic::Abc::IObject &object, ImportSettings &settings)
+    : AbcObjectReader(object, settings)
+{
+}
+
+bool AbcInstanceReader::valid() const
+{
+  // TODO(kevindietrich)
+  return true;
+}
+
+bool AbcInstanceReader::accepts_object_type(
+    const Alembic::AbcCoreAbstract::ObjectHeader & /*alembic_header*/,
+    const Object *const /*ob*/,
+    const char ** /*err_str*/) const
+{
+  /* TODO(kevindietrich) */
+  return true;
+}
+
+void AbcInstanceReader::readObjectData(Main *bmain,
+                                       const AbcReaderManager &manager,
+                                       const Alembic::Abc::ISampleSelector & /* sample_sel */)
+{
+  /* For reference on duplication, see ED_object_add_duplicate_linked.
+   *
+   * In this function, we only duplicate the object, as the rest (adding to view layer, tagging the
+   * depsgraph, etc.) is done at the end of the import.
+   */
+
+  Object *ob = manager.get_blender_object_for_path(m_iobject.instanceSourcePath());
+  BLI_assert(ob);
+  /* 0 = linked */
+  uint dupflag = 0;
+  uint duplicate_options = LIB_ID_DUPLICATE_IS_SUBPROCESS | LIB_ID_DUPLICATE_IS_ROOT_ID;
+
+  m_object = static_cast<Object *>(
+      ID_NEW_SET(ob, BKE_object_duplicate(bmain, ob, dupflag, duplicate_options)));
+
+  /* link own references to the newly duplicated data T26816. */
+  BKE_libblock_relink_to_newid(bmain, &m_object->id, 0);
+}
+
+}  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_instance.h

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+/** \file
+ * \ingroup balembic
+ */
+
+#include "abc_reader_object.h"
+
+namespace blender::io::alembic {
+
+class AbcInstanceReader final : public AbcObjectReader {
+ public:
+  AbcInstanceReader(const Alembic::Abc::IObject &object, ImportSettings &settings);
+
+  bool valid() const override;
+
+  bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+                           const Object *const ob,
+                           const char **err_str) const override;
+
+  void readObjectData(Main *bmain,
+                      const AbcReaderManager &manager,
+                      const Alembic::Abc::ISampleSelector &sample_sel) override;
+};
+
+}  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_manager.cc

@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup balembic
+ */
+
+#include "abc_reader_manager.h"
+
+#include "abc_reader_instance.h"
+
+namespace blender::io::alembic {
+
+AbcObjectReader *AbcReaderManager::create_instance_reader(Alembic::Abc::v12::IObject iobject,
+                                                          ImportSettings &settings)
+{
+  std::cerr << "Creating an instance reader...\n";
+  AbcObjectReader *reader = new AbcInstanceReader(iobject, settings);
+  m_instance_readers.push_back(reader);
+  m_readers_all.push_back(reader);
+  return reader;
+}
+
+Object *AbcReaderManager::get_blender_object_for_path(const std::string &path) const
+{
+  AbcObjectReader *reader = get_object_reader_for_path(path);
+  if (!reader) {
+    return nullptr;
+  }
+  return reader->object();
+}
+
+AbcObjectReader *AbcReaderManager::get_object_reader_for_path(const std::string &path) const
+{
+  MapIteratorType iter = m_readers_map.find(path);
+  if (iter == m_readers_map.end()) {
+    return nullptr;
+  }
+  return iter->second;
+}
+
+}  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_manager.h

@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+/** \file
+ * \ingroup balembic
+ */
+
+#include "abc_reader_object.h"
+
+namespace blender::io::alembic {
+
+class AbcReaderManager {
+  using MapType = std::map<std::string, AbcObjectReader *>;
+  using MapIteratorType = MapType::const_iterator;
+  std::map<std::string, AbcObjectReader *> m_readers_map{};
+
+  AbcObjectReader::ptr_vector m_readers;
+  AbcObjectReader::ptr_vector m_readers_all;
+  AbcObjectReader::ptr_vector m_instance_readers;
+
+ public:
+  template<typename ReaderType>
+  AbcObjectReader *create(Alembic::Abc::IObject iobject, ImportSettings &settings)
+  {
+    static_assert(
+        std::is_base_of_v<AbcObjectReader, ReaderType>,
+        "Trying to create a reader from a class which does not derive from AbcObjectReader !");
+
+    if (iobject.isInstanceRoot()) {
+      return create_instance_reader(iobject, settings);
+    }
+
+    ReaderType *reader = new ReaderType(iobject, settings);
+    m_readers_map[iobject.getFullName()] = reader;
+    m_readers.push_back(reader);
+    m_readers_all.push_back(reader);
+    return reader;
+  }
+
+  AbcObjectReader *create_instance_reader(Alembic::Abc::IObject iobject, ImportSettings &settings);
+
+  Object *get_blender_object_for_path(const std::string &path) const;
+
+  const AbcObjectReader::ptr_vector &all_readers() const
+  {
+    return m_readers_all;
+  }
+
+  const AbcObjectReader::ptr_vector &instance_readers() const
+  {
+    return m_instance_readers;
+  }
+
+  const AbcObjectReader::ptr_vector &data_readers() const
+  {
+    return m_readers;
+  }
+
+ private:
+  AbcObjectReader *get_object_reader_for_path(const std::string &path) const;
+};
+
+}  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_mesh.cc

@@ -24,7 +24,7 @@
 #include "BLI_listbase.h"
 #include "BLI_math_geom.h"
 
-#include "BKE_attribute.h"
+#include "BKE_geometry_set.hh"
 #include "BKE_main.h"
 #include "BKE_material.h"
 #include "BKE_mesh.h"
@@ -112,10 +112,6 @@ struct AbcMeshData {
 
   P3fArraySamplePtr positions;
   P3fArraySamplePtr ceil_positions;
-
-  AbcUvScope uv_scope;
-  V2fArraySamplePtr uvs;
-  UInt32ArraySamplePtr uvs_indices;
 };
 
 static void read_mverts_interp(MVert *mverts,
@@ -175,21 +171,12 @@ static void read_mpolys(CDStreamConfig &config, const AbcMeshData &mesh_data)
 {
   MPoly *mpolys = config.mpoly;
   MLoop *mloops = config.mloop;
-  MLoopUV *mloopuvs = config.mloopuv;
 
   const Int32ArraySamplePtr &face_indices = mesh_data.face_indices;
   const Int32ArraySamplePtr &face_counts = mesh_data.face_counts;
-  const V2fArraySamplePtr &uvs = mesh_data.uvs;
-  const size_t uvs_size = uvs == nullptr ? 0 : uvs->size();
 
-  const UInt32ArraySamplePtr &uvs_indices = mesh_data.uvs_indices;
-
-  const bool do_uvs = (mloopuvs && uvs && uvs_indices);
-  const bool do_uvs_per_loop = do_uvs && mesh_data.uv_scope == ABC_UV_SCOPE_LOOP;
-  BLI_assert(!do_uvs || mesh_data.uv_scope != ABC_UV_SCOPE_NONE);
   unsigned int loop_index = 0;
   unsigned int rev_loop_index = 0;
-  unsigned int uv_index = 0;
   bool seen_invalid_geometry = false;
 
   for (int i = 0; i < face_counts->size(); i++) {
@@ -217,19 +204,6 @@ static void read_mpolys(CDStreamConfig &config, const AbcMeshData &mesh_data)
         seen_invalid_geometry = true;
       }
       last_vertex_index = loop.v;
-
-      if (do_uvs) {
-        MLoopUV &loopuv = mloopuvs[rev_loop_index];
-        uv_index = (*uvs_indices)[do_uvs_per_loop ? loop_index : loop.v];
-
-        /* Some Alembic files are broken (or at least export UVs in a way we don't expect). */
-        if (uv_index >= uvs_size) {
-          continue;
-        }
-
-        loopuv.uv[0] = (*uvs)[uv_index][0];
-        loopuv.uv[1] = (*uvs)[uv_index][1];
-      }
     }
   }
 
@@ -337,68 +311,6 @@ static void process_normals(CDStreamConfig &config,
   }
 }
 
-BLI_INLINE void read_uvs_params(CDStreamConfig &config,
-                                AbcMeshData &abc_data,
-                                const IV2fGeomParam &uv,
-                                const ISampleSelector &selector)
-{
-  if (!uv.valid()) {
-    return;
-  }
-
-  IV2fGeomParam::Sample uvsamp;
-  uv.getIndexed(uvsamp, selector);
-
-  UInt32ArraySamplePtr uvs_indices = uvsamp.getIndices();
-
-  const AbcUvScope uv_scope = get_uv_scope(uv.getScope(), config, uvs_indices);
-
-  if (uv_scope == ABC_UV_SCOPE_NONE) {
-    return;
-  }
-
-  abc_data.uv_scope = uv_scope;
-  abc_data.uvs = uvsamp.getVals();
-  abc_data.uvs_indices = uvs_indices;
-
-  std::string name = Alembic::Abc::GetSourceName(uv.getMetaData());
-
-  /* According to the convention, primary UVs should have had their name
-   * set using Alembic::Abc::SetSourceName, but you can't expect everyone
-   * to follow it! :) */
-  if (name.empty()) {
-    name = uv.getName();
-  }
-
-  void *cd_ptr = config.add_customdata_cb(config.mesh, name.c_str(), CD_MLOOPUV);
-  config.mloopuv = static_cast<MLoopUV *>(cd_ptr);
-}
-
-static void *add_customdata_cb(Mesh *mesh, const char *name, int data_type)
-{
-  CustomDataType cd_data_type = static_cast<CustomDataType>(data_type);
-  void *cd_ptr;
-  CustomData *loopdata;
-  int numloops;
-
-  /* unsupported custom data type -- don't do anything. */
-  if (!ELEM(cd_data_type, CD_MLOOPUV, CD_MLOOPCOL)) {
-    return nullptr;
-  }
-
-  loopdata = &mesh->ldata;
-  cd_ptr = CustomData_get_layer_named(loopdata, cd_data_type, name);
-  if (cd_ptr != nullptr) {
-    /* layer already exists, so just return it. */
-    return cd_ptr;
-  }
-
-  /* Create a new layer. */
-  numloops = mesh->totloop;
-  cd_ptr = CustomData_add_layer_named(loopdata, cd_data_type, CD_DEFAULT, nullptr, numloops, name);
-  return cd_ptr;
-}
-
 static void get_weight_and_index(CDStreamConfig &config,
                                  Alembic::AbcCoreAbstract::TimeSamplingPtr time_sampling,
                                  size_t samples_number)
@@ -411,65 +323,7 @@ static void get_weight_and_index(CDStreamConfig &config,
   config.ceil_index = i1;
 }
 
-static V3fArraySamplePtr get_velocity_prop(const ICompoundProperty &schema,
-                                           const ISampleSelector &selector,
-                                           const std::string &name)
-{
-  for (size_t i = 0; i < schema.getNumProperties(); i++) {
-    const PropertyHeader &header = schema.getPropertyHeader(i);
-
-    if (header.isCompound()) {
-      const ICompoundProperty &prop = ICompoundProperty(schema, header.getName());
-
-      if (has_property(prop, name)) {
-        /* Header cannot be null here, as its presence is checked via has_property, so it is safe
-         * to dereference. */
-        const PropertyHeader *header = prop.getPropertyHeader(name);
-        if (!IV3fArrayProperty::matches(*header)) {
-          continue;
-        }
-
-        const IV3fArrayProperty &velocity_prop = IV3fArrayProperty(prop, name, 0);
-        if (velocity_prop) {
-          return velocity_prop.getValue(selector);
-        }
-      }
-    }
-    else if (header.isArray()) {
-      if (header.getName() == name && IV3fArrayProperty::matches(header)) {
-        const IV3fArrayProperty &velocity_prop = IV3fArrayProperty(schema, name, 0);
-        return velocity_prop.getValue(selector);
-      }
-    }
-  }
-
-  return V3fArraySamplePtr();
-}
-
-static void read_velocity(const V3fArraySamplePtr &velocities,
-                          const CDStreamConfig &config,
-                          const float velocity_scale)
-{
-  const int num_velocity_vectors = static_cast<int>(velocities->size());
-  if (num_velocity_vectors != config.mesh->totvert) {
-    /* Files containing videogrammetry data may be malformed and export velocity data on missing
-     * frames (most likely by copying the last valid data). */
-    return;
-  }
-
-  CustomDataLayer *velocity_layer = BKE_id_attribute_new(
-      &config.mesh->id, "velocity", CD_PROP_FLOAT3, ATTR_DOMAIN_POINT, nullptr);
-  float(*velocity)[3] = (float(*)[3])velocity_layer->data;
-
-  for (int i = 0; i < num_velocity_vectors; i++) {
-    const Imath::V3f &vel_in = (*velocities)[i];
-    copy_zup_from_yup(velocity[i], vel_in.getValue());
-    mul_v3_fl(velocity[i], velocity_scale);
-  }
-}
-
-static void read_mesh_sample(const std::string &iobject_full_name,
-                             ImportSettings *settings,
+static void read_mesh_sample(ImportSettings *settings,
                              const IPolyMeshSchema &schema,
                              const ISampleSelector &selector,
                              CDStreamConfig &config)
@@ -489,13 +343,8 @@ static void read_mesh_sample(const std::string &iobject_full_name,
     abc_mesh_data.ceil_positions = ceil_sample.getPositions();
   }
 
-  if ((settings->read_flag & MOD_MESHSEQ_READ_UV) != 0) {
-    read_uvs_params(config, abc_mesh_data, schema.getUVsParam(), selector);
-  }
-
   if ((settings->read_flag & MOD_MESHSEQ_READ_VERT) != 0) {
     read_mverts(config, abc_mesh_data);
-    read_generated_coordinates(schema.getArbGeomParams(), config, selector);
   }
 
   if ((settings->read_flag & MOD_MESHSEQ_READ_POLY) != 0) {
@@ -503,25 +352,21 @@ static void read_mesh_sample(const std::string &iobject_full_name,
     process_normals(config, schema.getNormalsParam(), selector);
   }
 
-  if ((settings->read_flag & (MOD_MESHSEQ_READ_UV | MOD_MESHSEQ_READ_COLOR)) != 0) {
-    read_custom_data(iobject_full_name, schema.getArbGeomParams(), config, selector);
-  }
-
-  if (!settings->velocity_name.empty() && settings->velocity_scale != 0.0f) {
-    V3fArraySamplePtr velocities = get_velocity_prop(schema, selector, settings->velocity_name);
-    if (velocities) {
-      read_velocity(velocities, config, settings->velocity_scale);
-    }
-  }
+  read_arbitrary_attributes(
+      config, schema, schema.getUVsParam(), selector, settings->velocity_scale);
 }
 
-CDStreamConfig get_config(Mesh *mesh, const bool use_vertex_interpolation)
+CDStreamConfig get_config(Mesh *mesh,
+                          const AttributeSelector *attr_selector,
+                          const std::string &iobject_full_name,
+                          const bool use_vertex_interpolation)
 {
   CDStreamConfig config;
 
   BLI_assert(mesh->mvert || mesh->totvert == 0);
 
   config.mesh = mesh;
+  config.id = &mesh->id;
   config.mvert = mesh->mvert;
   config.mloop = mesh->mloop;
   config.mpoly = mesh->mpoly;
@@ -529,8 +374,10 @@ CDStreamConfig get_config(Mesh *mesh, const bool use_vertex_interpolation)
   config.totloop = mesh->totloop;
   config.totpoly = mesh->totpoly;
   config.loopdata = &mesh->ldata;
-  config.add_customdata_cb = add_customdata_cb;
   config.use_vertex_interpolation = use_vertex_interpolation;
+  config.attr_selector = attr_selector;
+  config.iobject_full_name = iobject_full_name;
+  BKE_id_attribute_get_domains(config.id, config.domain_info);
 
   return config;
 }
@@ -553,39 +400,6 @@ bool AbcMeshReader::valid() const
   return m_schema.valid();
 }
 
-template<class typedGeomParam>
-bool is_valid_animated(const ICompoundProperty arbGeomParams, const PropertyHeader &prop_header)
-{
-  if (!typedGeomParam::matches(prop_header)) {
-    return false;
-  }
-
-  typedGeomParam geom_param(arbGeomParams, prop_header.getName());
-  return geom_param.valid() && !geom_param.isConstant();
-}
-
-static bool has_animated_geom_params(const ICompoundProperty arbGeomParams)
-{
-  if (!arbGeomParams.valid()) {
-    return false;
-  }
-
-  const int num_props = arbGeomParams.getNumProperties();
-  for (int i = 0; i < num_props; i++) {
-    const PropertyHeader &prop_header = arbGeomParams.getPropertyHeader(i);
-
-    /* These are interpreted as vertex colors later (see 'read_custom_data'). */
-    if (is_valid_animated<IC3fGeomParam>(arbGeomParams, prop_header)) {
-      return true;
-    }
-    if (is_valid_animated<IC4fGeomParam>(arbGeomParams, prop_header)) {
-      return true;
-    }
-  }
-
-  return false;
-}
-
 /* Specialization of #has_animations() as defined in abc_reader_object.h. */
 template<> bool has_animations(Alembic::AbcGeom::IPolyMeshSchema &schema, ImportSettings *settings)
 {
@@ -604,21 +418,30 @@ template<> bool has_animations(Alembic::AbcGeom::IPolyMeshSchema &schema, Import
   }
 
   ICompoundProperty arbGeomParams = schema.getArbGeomParams();
-  if (has_animated_geom_params(arbGeomParams)) {
+  if (has_animated_attributes(arbGeomParams)) {
     return true;
   }
 
   return false;
 }
 
-void AbcMeshReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel)
+void AbcMeshReader::readObjectData(Main *bmain,
+                                   const AbcReaderManager & /*manager*/,
+                                   const Alembic::Abc::ISampleSelector &sample_sel)
 {
   Mesh *mesh = BKE_mesh_add(bmain, m_data_name.c_str());
 
   m_object = BKE_object_add_only_object(bmain, OB_MESH, m_object_name.c_str());
   m_object->data = mesh;
 
-  Mesh *read_mesh = this->read_mesh(mesh, sample_sel, MOD_MESHSEQ_READ_ALL, "", 0.0f, nullptr);
+  /* Default AttributeSelector to ensure that at least UVs and vertex colors are read. To load
+   * other attributes, a modifier should be added as there are no clear conventions for them. */
+  ListBase lb = {nullptr, nullptr};
+  AttributeSelector attr_selector(&lb);
+  attr_selector.set_read_flags(MOD_MESHSEQ_READ_UV | MOD_MESHSEQ_READ_COLOR);
+
+  Mesh *read_mesh = this->read_mesh(
+      mesh, sample_sel, &attr_selector, MOD_MESHSEQ_READ_ALL, 0.0f, nullptr);
   if (read_mesh != mesh) {
     /* XXX FIXME: after 2.80; mesh->flag isn't copied by #BKE_mesh_nomain_to_mesh(). */
     /* read_mesh can be freed by BKE_mesh_nomain_to_mesh(), so get the flag before that happens. */
@@ -683,10 +506,31 @@ bool AbcMeshReader::topology_changed(Mesh *existing_mesh, const ISampleSelector
          face_indices->size() != existing_mesh->totloop;
 }
 
+void AbcMeshReader::read_geometry(GeometrySet &geometry_set,
+                                  const Alembic::Abc::ISampleSelector &sample_sel,
+                                  const AttributeSelector *attribute_selector,
+                                  int read_flag,
+                                  const float velocity_scale,
+                                  const char **err_str)
+{
+  Mesh *mesh = geometry_set.get_mesh_for_write();
+
+  if (mesh == nullptr) {
+    return;
+  }
+
+  Mesh *new_mesh = read_mesh(
+      mesh, sample_sel, attribute_selector, read_flag, velocity_scale, err_str);
+
+  if (new_mesh != mesh) {
+    geometry_set.replace_mesh(new_mesh);
+  }
+}
+
 Mesh *AbcMeshReader::read_mesh(Mesh *existing_mesh,
                                const ISampleSelector &sample_sel,
+                               const AttributeSelector *attribute_selector,
                                const int read_flag,
-                               const char *velocity_name,
                                const float velocity_scale,
                                const char **err_str)
 {
@@ -730,7 +574,6 @@ Mesh *AbcMeshReader::read_mesh(Mesh *existing_mesh,
   /* Only read point data when streaming meshes, unless we need to create new ones. */
   ImportSettings settings;
   settings.read_flag |= read_flag;
-  settings.velocity_name = velocity_name;
   settings.velocity_scale = velocity_scale;
 
   if (topology_changed(existing_mesh, sample_sel)) {
@@ -757,11 +600,12 @@ Mesh *AbcMeshReader::read_mesh(Mesh *existing_mesh,
 
   Mesh *mesh_to_export = new_mesh ? new_mesh : existing_mesh;
   const bool use_vertex_interpolation = read_flag & MOD_MESHSEQ_INTERPOLATE_VERTICES;
-  CDStreamConfig config = get_config(mesh_to_export, use_vertex_interpolation);
+  CDStreamConfig config = get_config(
+      mesh_to_export, attribute_selector, m_iobject.getFullName(), use_vertex_interpolation);
   config.time = sample_sel.getRequestedTime();
   config.modifier_error_message = err_str;
 
-  read_mesh_sample(m_iobject.getFullName(), &settings, m_schema, sample_sel, config);
+  read_mesh_sample(&settings, m_schema, sample_sel, config);
 
   if (new_mesh) {
     /* Here we assume that the number of materials doesn't change, i.e. that
@@ -848,8 +692,7 @@ BLI_INLINE MEdge *find_edge(MEdge *edges, int totedge, int v1, int v2)
   return nullptr;
 }
 
-static void read_subd_sample(const std::string &iobject_full_name,
-                             ImportSettings *settings,
+static void read_subd_sample(ImportSettings *settings,
                              const ISubDSchema &schema,
                              const ISampleSelector &selector,
                              CDStreamConfig &config)
@@ -869,10 +712,6 @@ static void read_subd_sample(const std::string &iobject_full_name,
     abc_mesh_data.ceil_positions = ceil_sample.getPositions();
   }
 
-  if ((settings->read_flag & MOD_MESHSEQ_READ_UV) != 0) {
-    read_uvs_params(config, abc_mesh_data, schema.getUVsParam(), selector);
-  }
-
   if ((settings->read_flag & MOD_MESHSEQ_READ_VERT) != 0) {
     read_mverts(config, abc_mesh_data);
   }
@@ -885,16 +724,8 @@ static void read_subd_sample(const std::string &iobject_full_name,
     process_no_normals(config);
   }
 
-  if ((settings->read_flag & (MOD_MESHSEQ_READ_UV | MOD_MESHSEQ_READ_COLOR)) != 0) {
-    read_custom_data(iobject_full_name, schema.getArbGeomParams(), config, selector);
-  }
-
-  if (!settings->velocity_name.empty() && settings->velocity_scale != 0.0f) {
-    V3fArraySamplePtr velocities = get_velocity_prop(schema, selector, settings->velocity_name);
-    if (velocities) {
-      read_velocity(velocities, config, settings->velocity_scale);
-    }
-  }
+  read_arbitrary_attributes(
+      config, schema, schema.getUVsParam(), selector, settings->velocity_scale);
 }
 
 static void read_vertex_creases(Mesh *mesh,
@@ -995,14 +826,23 @@ bool AbcSubDReader::accepts_object_type(
   return true;
 }
 
-void AbcSubDReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel)
+void AbcSubDReader::readObjectData(Main *bmain,
+                                   const AbcReaderManager & /*manager*/,
+                                   const Alembic::Abc::ISampleSelector &sample_sel)
 {
   Mesh *mesh = BKE_mesh_add(bmain, m_data_name.c_str());
 
   m_object = BKE_object_add_only_object(bmain, OB_MESH, m_object_name.c_str());
   m_object->data = mesh;
 
-  Mesh *read_mesh = this->read_mesh(mesh, sample_sel, MOD_MESHSEQ_READ_ALL, "", 0.0f, nullptr);
+  /* Default AttributeSelector to ensure that at least UVs and vertex colors are read. To load
+   * other attributes, a modifier should be added as there are no clear conventions for them. */
+  ListBase lb = {nullptr, nullptr};
+  AttributeSelector attr_selector(&lb);
+  attr_selector.set_read_flags(MOD_MESHSEQ_READ_UV | MOD_MESHSEQ_READ_COLOR);
+
+  Mesh *read_mesh = this->read_mesh(
+      mesh, sample_sel, &attr_selector, MOD_MESHSEQ_READ_ALL, 0.0f, nullptr);
   if (read_mesh != mesh) {
     BKE_mesh_nomain_to_mesh(read_mesh, mesh, m_object, &CD_MASK_EVERYTHING, true);
   }
@@ -1035,8 +875,8 @@ void AbcSubDReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelec
 
 Mesh *AbcSubDReader::read_mesh(Mesh *existing_mesh,
                                const ISampleSelector &sample_sel,
+                               const AttributeSelector *attribute_selector,
                                const int read_flag,
-                               const char *velocity_name,
                                const float velocity_scale,
                                const char **err_str)
 {
@@ -1064,7 +904,6 @@ Mesh *AbcSubDReader::read_mesh(Mesh *existing_mesh,
 
   ImportSettings settings;
   settings.read_flag |= read_flag;
-  settings.velocity_name = velocity_name;
   settings.velocity_scale = velocity_scale;
 
   if (existing_mesh->totvert != positions->size()) {
@@ -1092,11 +931,33 @@ Mesh *AbcSubDReader::read_mesh(Mesh *existing_mesh,
   /* Only read point data when streaming meshes, unless we need to create new ones. */
   Mesh *mesh_to_export = new_mesh ? new_mesh : existing_mesh;
   const bool use_vertex_interpolation = read_flag & MOD_MESHSEQ_INTERPOLATE_VERTICES;
-  CDStreamConfig config = get_config(mesh_to_export, use_vertex_interpolation);
+  CDStreamConfig config = get_config(
+      mesh_to_export, attribute_selector, m_iobject.getFullName(), use_vertex_interpolation);
   config.time = sample_sel.getRequestedTime();
-  read_subd_sample(m_iobject.getFullName(), &settings, m_schema, sample_sel, config);
+  read_subd_sample(&settings, m_schema, sample_sel, config);
 
   return mesh_to_export;
 }
 
+void AbcSubDReader::read_geometry(GeometrySet &geometry_set,
+                                  const Alembic::Abc::ISampleSelector &sample_sel,
+                                  const AttributeSelector *attribute_selector,
+                                  int read_flag,
+                                  const float velocity_scale,
+                                  const char **err_str)
+{
+  Mesh *mesh = geometry_set.get_mesh_for_write();
+
+  if (mesh == nullptr) {
+    return;
+  }
+
+  Mesh *new_mesh = read_mesh(
+      mesh, sample_sel, attribute_selector, read_flag, velocity_scale, err_str);
+
+  if (new_mesh != mesh) {
+    geometry_set.replace_mesh(new_mesh);
+  }
+}
+
 }  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_mesh.h

@@ -24,17 +24,20 @@ class AbcMeshReader final : public AbcObjectReader {
   bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
                            const Object *const ob,
                            const char **err_str) const override;
-  void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel) override;
+  void readObjectData(Main *bmain,
+                      const AbcReaderManager &manager,
+                      const Alembic::Abc::ISampleSelector &sample_sel) override;
 
-  struct Mesh *read_mesh(struct Mesh *existing_mesh,
-                         const Alembic::Abc::ISampleSelector &sample_sel,
-                         int read_flag,
-                         const char *velocity_name,
-                         float velocity_scale,
-                         const char **err_str) override;
   bool topology_changed(Mesh *existing_mesh,
                         const Alembic::Abc::ISampleSelector &sample_sel) override;
 
+  void read_geometry(GeometrySet &geometry_set,
+                     const Alembic::Abc::ISampleSelector &sample_sel,
+                     const AttributeSelector *attribute_selector,
+                     int read_flag,
+                     const float velocity_scale,
+                     const char **err_str) override;
+
  private:
   void readFaceSetsSample(Main *bmain,
                           Mesh *mesh,
@@ -44,6 +47,13 @@ class AbcMeshReader final : public AbcObjectReader {
                                 MPoly *mpoly,
                                 int totpoly,
                                 std::map<std::string, int> &r_mat_map);
+
+  struct Mesh *read_mesh(struct Mesh *existing_mesh,
+                         const Alembic::Abc::ISampleSelector &sample_sel,
+                         const AttributeSelector *attribute_selector,
+                         const int read_flag,
+                         const float velocity_scale,
+                         const char **err_str);
 };
 
 class AbcSubDReader final : public AbcObjectReader {
@@ -58,19 +68,33 @@ class AbcSubDReader final : public AbcObjectReader {
   bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
                            const Object *const ob,
                            const char **err_str) const override;
-  void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel) override;
+  void readObjectData(Main *bmain,
+                      const AbcReaderManager &manager,
+                      const Alembic::Abc::ISampleSelector &sample_sel) override;
+
+  void read_geometry(GeometrySet &geometry_set,
+                     const Alembic::Abc::ISampleSelector &sample_sel,
+                     const AttributeSelector *attribute_selector,
+                     int read_flag,
+                     const float velocity_scale,
+                     const char **err_str) override;
+
+ private:
   struct Mesh *read_mesh(struct Mesh *existing_mesh,
                          const Alembic::Abc::ISampleSelector &sample_sel,
-                         int read_flag,
-                         const char *velocity_name,
-                         float velocity_scale,
-                         const char **err_str) override;
+                         const AttributeSelector *attribute_selector,
+                         const int read_flag,
+                         const float velocity_scale,
+                         const char **err_str);
 };
 
 void read_mverts(Mesh &mesh,
                  const Alembic::AbcGeom::P3fArraySamplePtr positions,
                  const Alembic::AbcGeom::N3fArraySamplePtr normals);
 
-CDStreamConfig get_config(struct Mesh *mesh, bool use_vertex_interpolation);
+CDStreamConfig get_config(struct Mesh *mesh,
+                          const AttributeSelector *attr_selector,
+                          const std::string &iobject_full_name,
+                          bool use_vertex_interpolation);
 
 }  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_nurbs.cc

@@ -94,7 +94,9 @@ static bool set_knots(const FloatArraySamplePtr &knots, float *&nu_knots)
   return true;
 }
 
-void AbcNurbsReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel)
+void AbcNurbsReader::readObjectData(Main *bmain,
+                                    const AbcReaderManager & /*manager*/,
+                                    const Alembic::Abc::ISampleSelector &sample_sel)
 {
   Curve *cu = static_cast<Curve *>(BKE_curve_add(bmain, m_data_name.c_str(), OB_SURF));
   cu->actvert = CU_ACT_NONE;

source/blender/io/alembic/intern/abc_reader_nurbs.h

@@ -21,7 +21,9 @@ class AbcNurbsReader final : public AbcObjectReader {
                            const Object *const ob,
                            const char **err_str) const override;
 
-  void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel) override;
+  void readObjectData(Main *bmain,
+                      const AbcReaderManager &manager,
+                      const Alembic::Abc::ISampleSelector &sample_sel) override;
 
  private:
   void getNurbsPatches(const Alembic::Abc::IObject &obj);

source/blender/io/alembic/intern/abc_reader_object.cc

@@ -130,16 +130,6 @@ Imath::M44d get_matrix(const IXformSchema &schema, const float time)
   return s0.getMatrix();
 }
 
-struct Mesh *AbcObjectReader::read_mesh(struct Mesh *existing_mesh,
-                                        const Alembic::Abc::ISampleSelector &UNUSED(sample_sel),
-                                        int UNUSED(read_flag),
-                                        const char *UNUSED(velocity_name),
-                                        const float UNUSED(velocity_scale),
-                                        const char **UNUSED(err_str))
-{
-  return existing_mesh;
-}
-
 bool AbcObjectReader::topology_changed(Mesh * /*existing_mesh*/,
                                        const Alembic::Abc::ISampleSelector & /*sample_sel*/)
 {
@@ -148,6 +138,16 @@ bool AbcObjectReader::topology_changed(Mesh * /*existing_mesh*/,
   return false;
 }
 
+void AbcObjectReader::read_geometry(GeometrySet &UNUSED(geometry_set),
+                                    const Alembic::Abc::ISampleSelector &UNUSED(sample_sel),
+                                    const AttributeSelector *UNUSED(attribute_selector),
+                                    int UNUSED(read_flag),
+                                    const float UNUSED(velocity_scale),
+                                    const char **UNUSED(err_str))
+{
+  return;
+}
+
 void AbcObjectReader::setupObjectTransform(const float time)
 {
   bool is_constant = false;
@@ -166,16 +166,32 @@ void AbcObjectReader::setupObjectTransform(const float time)
   BKE_object_to_mat4(m_object, m_object->obmat);
 
   if (!is_constant || m_settings->always_add_cache_reader) {
-    bConstraint *con = BKE_constraint_add_for_object(
-        m_object, nullptr, CONSTRAINT_TYPE_TRANSFORM_CACHE);
-    bTransformCacheConstraint *data = static_cast<bTransformCacheConstraint *>(con->data);
-    BLI_strncpy(data->object_path, m_iobject.getFullName().c_str(), FILE_MAX);
-
-    data->cache_file = m_settings->cache_file;
-    id_us_plus(&data->cache_file->id);
+    bTransformCacheConstraint *constraint = getOrCreateConstraint();
+    BLI_strncpy(constraint->object_path, m_iobject.getFullName().c_str(), FILE_MAX);
   }
 }
 
+bTransformCacheConstraint *AbcObjectReader::getOrCreateConstraint()
+{
+  if (m_iobject.isInstanceRoot()) {
+    /* As this is an instance we may already have created a constraint when duplicating the source
+     * object, if so return it. Note that it is possible for an instance to have an animated
+     * transform, but not for the source object. */
+    bConstraint *constraint = static_cast<bConstraint *>(m_object->constraints.last);
+    if (constraint && constraint->type == CONSTRAINT_TYPE_TRANSFORM_CACHE) {
+      return static_cast<bTransformCacheConstraint *>(constraint->data);
+    }
+  }
+
+  /* Create a new constraint. */
+  bConstraint *constraint = BKE_constraint_add_for_object(
+      m_object, nullptr, CONSTRAINT_TYPE_TRANSFORM_CACHE);
+  bTransformCacheConstraint *data = static_cast<bTransformCacheConstraint *>(constraint->data);
+  data->cache_file = m_settings->cache_file;
+  id_us_plus(&data->cache_file->id);
+  return data;
+}
+
 Alembic::AbcGeom::IXform AbcObjectReader::xform()
 {
   /* Check that we have an empty object (locator, bone head/tail...). */

source/blender/io/alembic/intern/abc_reader_object.h

@@ -10,7 +10,9 @@
 
 #include "DNA_ID.h"
 
+struct bTransformCacheConstraint;
 struct CacheFile;
+struct GeometrySet;
 struct Main;
 struct Mesh;
 struct Object;
@@ -19,6 +21,9 @@ using Alembic::AbcCoreAbstract::chrono_t;
 
 namespace blender::io::alembic {
 
+class AbcReaderManager;
+class AttributeSelector;
+
 struct ImportSettings {
   bool do_convert_mat;
   float conversion_mat[4][4];
@@ -37,7 +42,6 @@ struct ImportSettings {
   int read_flag;
 
   /* From CacheFile and MeshSeqCacheModifierData */
-  std::string velocity_name;
   float velocity_scale;
 
   bool validate_meshes;
@@ -55,7 +59,6 @@ struct ImportSettings {
         sequence_len(1),
         sequence_offset(0),
         read_flag(0),
-        velocity_name(""),
         velocity_scale(1.0f),
         validate_meshes(false),
         always_add_cache_reader(false),
@@ -131,17 +134,20 @@ class AbcObjectReader {
                                    const Object *const ob,
                                    const char **err_str) const = 0;
 
-  virtual void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel) = 0;
+  virtual void readObjectData(Main *bmain,
+                              const AbcReaderManager &manager,
+                              const Alembic::Abc::ISampleSelector &sample_sel) = 0;
 
-  virtual struct Mesh *read_mesh(struct Mesh *mesh,
-                                 const Alembic::Abc::ISampleSelector &sample_sel,
-                                 int read_flag,
-                                 const char *velocity_name,
-                                 float velocity_scale,
-                                 const char **err_str);
   virtual bool topology_changed(Mesh *existing_mesh,
                                 const Alembic::Abc::ISampleSelector &sample_sel);
 
+  virtual void read_geometry(GeometrySet &geometry_set,
+                             const Alembic::Abc::ISampleSelector &sample_sel,
+                             const AttributeSelector *attribute_selector,
+                             int read_flag,
+                             const float velocity_scale,
+                             const char **err_str);
+
   /** Reads the object matrix and sets up an object transform if animated. */
   void setupObjectTransform(float time);
 
@@ -159,6 +165,9 @@ class AbcObjectReader {
  protected:
   /** Determine whether we can inherit our parent's XForm. */
   void determine_inherits_xform();
+
+ private:
+  bTransformCacheConstraint *getOrCreateConstraint();
 };
 
 Imath::M44d get_matrix(const Alembic::AbcGeom::IXformSchema &schema, float time);

source/blender/io/alembic/intern/abc_reader_points.cc

@@ -6,6 +6,7 @@
  */
 
 #include "abc_reader_points.h"
+#include "abc_axis_conversion.h"
 #include "abc_reader_mesh.h"
 #include "abc_reader_transform.h"
 #include "abc_util.h"
@@ -13,15 +14,21 @@
 #include "DNA_mesh_types.h"
 #include "DNA_modifier_types.h"
 #include "DNA_object_types.h"
+#include "DNA_pointcloud_types.h"
 
 #include "BKE_customdata.h"
+#include "BKE_geometry_set.hh"
+#include "BKE_lib_id.h"
 #include "BKE_mesh.h"
 #include "BKE_object.h"
+#include "BKE_pointcloud.h"
 
 using Alembic::AbcGeom::kWrapExisting;
 using Alembic::AbcGeom::N3fArraySamplePtr;
 using Alembic::AbcGeom::P3fArraySamplePtr;
 
+using namespace Alembic::AbcGeom;
+
 using Alembic::AbcGeom::ICompoundProperty;
 using Alembic::AbcGeom::IN3fArrayProperty;
 using Alembic::AbcGeom::IPoints;
@@ -55,7 +62,7 @@ bool AbcPointsReader::accepts_object_type(
     return false;
   }
 
-  if (ob->type != OB_MESH) {
+  if (ob->type != OB_POINTCLOUD) {
     *err_str = "Object type mismatch, Alembic object path points to Points.";
     return false;
   }
@@ -63,58 +70,89 @@ bool AbcPointsReader::accepts_object_type(
   return true;
 }
 
-void AbcPointsReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel)
+void AbcPointsReader::readObjectData(Main *bmain,
+                                     const AbcReaderManager & /*manager*/,
+                                     const Alembic::Abc::ISampleSelector &sample_sel)
 {
-  Mesh *mesh = BKE_mesh_add(bmain, m_data_name.c_str());
-  Mesh *read_mesh = this->read_mesh(mesh, sample_sel, 0, "", 0.0f, nullptr);
+  PointCloud *point_cloud = static_cast<PointCloud *>(
+      BKE_pointcloud_add_default(bmain, m_data_name.c_str()));
 
-  if (read_mesh != mesh) {
-    BKE_mesh_nomain_to_mesh(read_mesh, mesh, m_object, &CD_MASK_MESH, true);
+  GeometrySet geometry_set = GeometrySet::create_with_pointcloud(point_cloud,
+                                                                 GeometryOwnershipType::Editable);
+  read_geometry(geometry_set, sample_sel, nullptr, 0, 0.0f, nullptr);
+
+  PointCloud *read_point_cloud =
+      geometry_set.get_component_for_write<PointCloudComponent>().release();
+
+  if (read_point_cloud != point_cloud) {
+    BKE_pointcloud_nomain_to_pointcloud(read_point_cloud, point_cloud, true);
   }
 
-  if (m_settings->validate_meshes) {
-    BKE_mesh_validate(mesh, false, false);
-  }
-
-  m_object = BKE_object_add_only_object(bmain, OB_MESH, m_object_name.c_str());
-  m_object->data = mesh;
+  m_object = BKE_object_add_only_object(bmain, OB_POINTCLOUD, m_object_name.c_str());
+  m_object->data = point_cloud;
 
   if (m_settings->always_add_cache_reader || has_animations(m_schema, m_settings)) {
     addCacheModifier();
   }
 }
 
-void read_points_sample(const IPointsSchema &schema,
-                        const ISampleSelector &selector,
-                        CDStreamConfig &config)
+static void read_points_interp(const P3fArraySamplePtr positions,
+                               const P3fArraySamplePtr ceil_positions,
+                               const float weight,
+                               float3 *r_points)
+{
+  float3 tmp;
+  for (size_t i = 0; i < positions->size(); i++) {
+    const Imath::V3f &floor_pos = (*positions)[i];
+    const Imath::V3f &ceil_pos = (*ceil_positions)[i];
+    interp_v3_v3v3(tmp, floor_pos.getValue(), ceil_pos.getValue(), weight);
+    copy_zup_from_yup(r_points[i], (*positions)[i].getValue());
+  }
+}
+
+static void read_points(const P3fArraySamplePtr positions, float3 *r_points)
+{
+  for (size_t i = 0; i < positions->size(); i++) {
+    copy_zup_from_yup(r_points[i], (*positions)[i].getValue());
+  }
+}
+
+static void read_points_sample(const IPointsSchema &schema,
+                               const ISampleSelector &selector,
+                               CDStreamConfig &config,
+                               float3 *r_points)
 {
   Alembic::AbcGeom::IPointsSchema::Sample sample = schema.getValue(selector);
 
   const P3fArraySamplePtr &positions = sample.getPositions();
 
   ICompoundProperty prop = schema.getArbGeomParams();
-  N3fArraySamplePtr vnormals;
 
-  if (has_property(prop, "N")) {
-    const Alembic::Util::uint32_t itime = static_cast<Alembic::Util::uint32_t>(
-        selector.getRequestedTime());
-    const IN3fArrayProperty &normals_prop = IN3fArrayProperty(prop, "N", itime);
+  Alembic::AbcGeom::index_t i0, i1;
+  const float weight = get_weight_and_index(
+      config.time, schema.getTimeSampling(), schema.getNumSamples(), i0, i1);
 
-    if (normals_prop) {
-      vnormals = normals_prop.getValue(selector);
-    }
+  if (config.use_vertex_interpolation && weight != 0.0f) {
+    Alembic::AbcGeom::IPointsSchema::Sample ceil_sample;
+    schema.get(ceil_sample, Alembic::Abc::ISampleSelector(i1));
+    P3fArraySamplePtr ceil_positions = ceil_sample.getPositions();
+
+    read_points_interp(positions, ceil_positions, weight, r_points);
+    return;
   }
 
-  read_mverts(*config.mesh, positions, vnormals);
+  read_points(positions, r_points);
 }
 
-struct Mesh *AbcPointsReader::read_mesh(struct Mesh *existing_mesh,
-                                        const ISampleSelector &sample_sel,
-                                        int read_flag,
-                                        const char * /*velocity_name*/,
-                                        const float /*velocity_scale*/,
-                                        const char **err_str)
+void AbcPointsReader::read_geometry(GeometrySet &geometry_set,
+                                    const Alembic::Abc::ISampleSelector &sample_sel,
+                                    const AttributeSelector *attribute_selector,
+                                    int read_flag,
+                                    const float velocity_scale,
+                                    const char **err_str)
 {
+  assert(geometry_set.has_pointcloud());
+
   IPointsSchema::Sample sample;
   try {
     sample = m_schema.getValue(sample_sel);
@@ -126,23 +164,64 @@ struct Mesh *AbcPointsReader::read_mesh(struct Mesh *existing_mesh,
            m_schema.getName().c_str(),
            sample_sel.getRequestedTime(),
            ex.what());
-    return existing_mesh;
+    return;
   }
 
+  PointCloud *existing_point_cloud = geometry_set.get_pointcloud_for_write();
+  PointCloud *point_cloud = existing_point_cloud;
+
   const P3fArraySamplePtr &positions = sample.getPositions();
 
-  Mesh *new_mesh = nullptr;
+  const IFloatGeomParam widths_param = m_schema.getWidthsParam();
+  FloatArraySamplePtr radiuses;
 
-  if (existing_mesh->totvert != positions->size()) {
-    new_mesh = BKE_mesh_new_nomain(positions->size(), 0, 0, 0, 0);
+  if (widths_param.valid()) {
+    IFloatGeomParam::Sample wsample = widths_param.getExpandedValue(sample_sel);
+    radiuses = wsample.getVals();
   }
 
-  Mesh *mesh_to_export = new_mesh ? new_mesh : existing_mesh;
-  const bool use_vertex_interpolation = read_flag & MOD_MESHSEQ_INTERPOLATE_VERTICES;
-  CDStreamConfig config = get_config(mesh_to_export, use_vertex_interpolation);
-  read_points_sample(m_schema, sample_sel, config);
+  if (point_cloud->totpoint != positions->size()) {
+    point_cloud = BKE_pointcloud_new_nomain(positions->size());
+  }
 
-  return mesh_to_export;
+  CDStreamConfig config;
+  config.id = &point_cloud->id;
+  BKE_id_attribute_get_domains(config.id, config.domain_info);
+  config.attr_selector = attribute_selector;
+  config.time = sample_sel.getRequestedTime();
+  config.use_vertex_interpolation = (read_flag & MOD_MESHSEQ_INTERPOLATE_VERTICES) != 0;
+  config.modifier_error_message = err_str;
+
+  read_points_sample(m_schema, sample_sel, config, reinterpret_cast<float3 *>(point_cloud->co));
+
+  if (radiuses) {
+    for (size_t i = 0; i < radiuses->size(); i++) {
+      point_cloud->radius[i] = (*radiuses)[i];
+    }
+  }
+  else {
+    for (int i = 0; i < point_cloud->totpoint; i++) {
+      point_cloud->radius[i] = 0.01f;
+    }
+  }
+
+  UInt64ArraySamplePtr ids = sample.getIds();
+  if (ids && ids->size() == positions->size()) {
+    CustomDataLayer *ids_layer = BKE_id_attribute_ensure(
+        &point_cloud->id, "ids", CD_PROP_INT32, ATTR_DOMAIN_POINT, nullptr);
+    int *ids_layer_data = static_cast<int *>(ids_layer->data);
+
+    for (size_t i = 0; i < ids->size(); i++) {
+      ids_layer_data[i] = static_cast<int>((*ids)[i]);
+    }
+  }
+
+  /* Attributes */
+  read_arbitrary_attributes(config, m_schema, {}, sample_sel, velocity_scale);
+
+  if (point_cloud != existing_point_cloud) {
+    geometry_set.replace_pointcloud(point_cloud);
+  }
 }
 
 }  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_points.h

@@ -23,18 +23,16 @@ class AbcPointsReader final : public AbcObjectReader {
                            const Object *const ob,
                            const char **err_str) const override;
 
-  void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel) override;
+  void readObjectData(Main *bmain,
+                      const AbcReaderManager &manager,
+                      const Alembic::Abc::ISampleSelector &sample_sel) override;
 
-  struct Mesh *read_mesh(struct Mesh *existing_mesh,
-                         const Alembic::Abc::ISampleSelector &sample_sel,
-                         int read_flag,
-                         const char *velocity_name,
-                         float velocity_scale,
-                         const char **err_str) override;
+  void read_geometry(GeometrySet &geometry_set,
+                     const Alembic::Abc::ISampleSelector &sample_sel,
+                     const AttributeSelector *attribute_selector,
+                     int read_flag,
+                     const float velocity_scale,
+                     const char **err_str) override;
 };
 
-void read_points_sample(const Alembic::AbcGeom::IPointsSchema &schema,
-                        const Alembic::AbcGeom::ISampleSelector &selector,
-                        CDStreamConfig &config);
-
 }  // namespace blender::io::alembic

source/blender/io/alembic/intern/abc_reader_transform.cc

@@ -55,7 +55,9 @@ bool AbcEmptyReader::accepts_object_type(
   return true;
 }
 
-void AbcEmptyReader::readObjectData(Main *bmain, const ISampleSelector &UNUSED(sample_sel))
+void AbcEmptyReader::readObjectData(Main *bmain,
+                                    const AbcReaderManager & /*manager*/,
+                                    const ISampleSelector &UNUSED(sample_sel))
 {
   m_object = BKE_object_add_only_object(bmain, OB_EMPTY, m_object_name.c_str());
   m_object->data = nullptr;

source/blender/io/alembic/intern/abc_reader_transform.h

@@ -22,7 +22,9 @@ class AbcEmptyReader final : public AbcObjectReader {
                            const Object *const ob,
                            const char **err_str) const override;
 
-  void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel) override;
+  void readObjectData(Main *bmain,
+                      const AbcReaderManager &manager,
+                      const Alembic::Abc::ISampleSelector &sample_sel) override;
 };
 
 }  // namespace blender::io::alembic

source/blender/io/alembic/intern/alembic_capi.cc

@@ -13,6 +13,7 @@
 #include "abc_reader_archive.h"
 #include "abc_reader_camera.h"
 #include "abc_reader_curves.h"
+#include "abc_reader_manager.h"
 #include "abc_reader_mesh.h"
 #include "abc_reader_nurbs.h"
 #include "abc_reader_points.h"
@@ -211,7 +212,7 @@ static void find_iobject(const IObject &object, IObject &ret, const std::string
  * Generates an AbcObjectReader for this Alembic object and its children.
  *
  * \param object: The Alembic IObject to visit.
- * \param readers: The created AbcObjectReader * will be appended to this vector.
+ * \param manager: The manager responsible for creating the readers.
  * \param settings: Import settings, not used directly but passed to the
  *                 AbcObjectReader subclass constructors.
  * \param r_assign_as_parent: Return parameter, contains a list of reader
@@ -229,7 +230,7 @@ static void find_iobject(const IObject &object, IObject &ret, const std::string
  * them in sync. */
 static std::pair<bool, AbcObjectReader *> visit_object(
     const IObject &object,
-    AbcObjectReader::ptr_vector &readers,
+    AbcReaderManager &manager,
     ImportSettings &settings,
     AbcObjectReader::ptr_vector &r_assign_as_parent)
 {
@@ -254,7 +255,7 @@ static std::pair<bool, AbcObjectReader *> visit_object(
 
     /* TODO: When we only support C++11, use std::tie() instead. */
     std::pair<bool, AbcObjectReader *> child_result;
-    child_result = visit_object(ichild, readers, settings, assign_as_parent);
+    child_result = visit_object(ichild, manager, settings, assign_as_parent);
 
     bool child_claims_this_object = child_result.first;
     AbcObjectReader *child_reader = child_result.second;
@@ -299,15 +300,15 @@ static std::pair<bool, AbcObjectReader *> visit_object(
     }
 
     if (create_empty) {
-      reader = new AbcEmptyReader(object, settings);
+      reader = manager.create<AbcEmptyReader>(object, settings);
     }
   }
   else if (IPolyMesh::matches(md)) {
-    reader = new AbcMeshReader(object, settings);
+    reader = manager.create<AbcMeshReader>(object, settings);
     parent_is_part_of_this_object = true;
   }
   else if (ISubD::matches(md)) {
-    reader = new AbcSubDReader(object, settings);
+    reader = manager.create<AbcSubDReader>(object, settings);
     parent_is_part_of_this_object = true;
   }
   else if (INuPatch::matches(md)) {
@@ -318,16 +319,16 @@ static std::pair<bool, AbcObjectReader *> visit_object(
      * Blender. Need to figure out exactly how these points are
      * duplicated, in all cases (cyclic U, cyclic V, and cyclic UV).
      * Until this is fixed, disabling NURBS reading. */
-    reader = new AbcNurbsReader(object, settings);
+    reader = manager.create<AbcNurbsReader>(object, settings);
     parent_is_part_of_this_object = true;
 #endif
   }
   else if (ICamera::matches(md)) {
-    reader = new AbcCameraReader(object, settings);
+    reader = manager.create<AbcCameraReader>(object, settings);
     parent_is_part_of_this_object = true;
   }
   else if (IPoints::matches(md)) {
-    reader = new AbcPointsReader(object, settings);
+    reader = manager.create<AbcPointsReader>(object, settings);
     parent_is_part_of_this_object = true;
   }
   else if (IMaterial::matches(md)) {
@@ -340,7 +341,7 @@ static std::pair<bool, AbcObjectReader *> visit_object(
     /* Pass, those are handled in the mesh reader. */
   }
   else if (ICurves::matches(md)) {
-    reader = new AbcCurveReader(object, settings);
+    reader = manager.create<AbcCurveReader>(object, settings);
     parent_is_part_of_this_object = true;
   }
   else {
@@ -353,7 +354,6 @@ static std::pair<bool, AbcObjectReader *> visit_object(
      * not claimed as part of any child Alembic object. */
     BLI_assert(claiming_child_readers.empty());
 
-    readers.push_back(reader);
     reader->incref();
 
     CacheObjectPath *abc_path = static_cast<CacheObjectPath *>(
@@ -423,7 +423,7 @@ struct ImportJobData {
   ImportSettings settings;
 
   ArchiveReader *archive;
-  std::vector<AbcObjectReader *> readers;
+  AbcReaderManager reader_manager;
 
   short *stop;
   short *do_update;
@@ -475,7 +475,8 @@ static void import_startjob(void *user_data, short *stop, short *do_update, floa
 
   /* Parse Alembic Archive. */
   AbcObjectReader::ptr_vector assign_as_parent;
-  visit_object(archive->getTop(), data->readers, data->settings, assign_as_parent);
+  IObject root = archive->getTop();
+  visit_object(archive->getTop(), data->reader_manager, data->settings, assign_as_parent);
 
   /* There shouldn't be any orphans. */
   BLI_assert(assign_as_parent.empty());
@@ -490,19 +491,16 @@ static void import_startjob(void *user_data, short *stop, short *do_update, floa
 
   /* Create objects and set scene frame range. */
 
-  const float size = static_cast<float>(data->readers.size());
+  const float size = static_cast<float>(data->reader_manager.all_readers().size());
   size_t i = 0;
 
   chrono_t min_time = std::numeric_limits<chrono_t>::max();
   chrono_t max_time = std::numeric_limits<chrono_t>::min();
 
   ISampleSelector sample_sel(0.0f);
-  std::vector<AbcObjectReader *>::iterator iter;
-  for (iter = data->readers.begin(); iter != data->readers.end(); ++iter) {
-    AbcObjectReader *reader = *iter;
-
+  for (AbcObjectReader *reader : data->reader_manager.data_readers()) {
     if (reader->valid()) {
-      reader->readObjectData(data->bmain, sample_sel);
+      reader->readObjectData(data->bmain, data->reader_manager, sample_sel);
 
       min_time = std::min(min_time, reader->minTime());
       max_time = std::max(max_time, reader->maxTime());
@@ -537,8 +535,7 @@ static void import_startjob(void *user_data, short *stop, short *do_update, floa
   }
 
   /* Setup parenthood. */
-  for (iter = data->readers.begin(); iter != data->readers.end(); ++iter) {
-    const AbcObjectReader *reader = *iter;
+  for (AbcObjectReader *reader : data->reader_manager.data_readers()) {
     const AbcObjectReader *parent_reader = reader->parent_reader;
     Object *ob = reader->object();
 
@@ -552,8 +549,7 @@ static void import_startjob(void *user_data, short *stop, short *do_update, floa
 
   /* Setup transformations and constraints. */
   i = 0;
-  for (iter = data->readers.begin(); iter != data->readers.end(); ++iter) {
-    AbcObjectReader *reader = *iter;
+  for (AbcObjectReader *reader : data->reader_manager.data_readers()) {
     reader->setupObjectTransform(0.0f);
 
     *data->progress = 0.7f + 0.3f * (++i / size);
@@ -572,12 +568,10 @@ static void import_endjob(void *user_data)
 
   ImportJobData *data = static_cast<ImportJobData *>(user_data);
 
-  std::vector<AbcObjectReader *>::iterator iter;
-
   /* Delete objects on cancellation. */
   if (data->was_cancelled) {
-    for (iter = data->readers.begin(); iter != data->readers.end(); ++iter) {
-      Object *ob = (*iter)->object();
+    for (AbcObjectReader *reader : data->reader_manager.all_readers()) {
+      Object *ob = reader->object();
 
       /* It's possible that cancellation occurred between the creation of
        * the reader and the creation of the Blender object. */
@@ -598,8 +592,8 @@ static void import_endjob(void *user_data)
 
     lc = BKE_layer_collection_get_active(view_layer);
 
-    for (iter = data->readers.begin(); iter != data->readers.end(); ++iter) {
-      Object *ob = (*iter)->object();
+    for (AbcObjectReader *reader : data->reader_manager.data_readers()) {
+      Object *ob = reader->object();
 
       BKE_collection_object_add(data->bmain, lc->collection, ob);
 
@@ -614,6 +608,24 @@ static void import_endjob(void *user_data)
                                ID_RECALC_BASE_FLAGS);
     }
 
+    /* Finally, create instances. */
+    for (AbcObjectReader *reader : data->reader_manager.instance_readers()) {
+      if (!reader->valid()) {
+        continue;
+      }
+
+      reader->readObjectData(data->bmain, data->reader_manager, {});
+      /* We assume that the instance's parent is the same as that of the source object, so we do
+       * not setup parenthood. */
+      reader->setupObjectTransform(0.0f);
+
+      Object *ob = reader->object();
+      BKE_collection_object_add(data->bmain, lc->collection, ob);
+      DEG_id_tag_update(&ob->id, ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY);
+
+      BKE_main_id_newptr_and_tag_clear(data->bmain);
+    }
+
     DEG_id_tag_update(&data->scene->id, ID_RECALC_BASE_FLAGS);
     DEG_relations_tag_update(data->bmain);
 
@@ -624,8 +636,7 @@ static void import_endjob(void *user_data)
     }
   }
 
-  for (iter = data->readers.begin(); iter != data->readers.end(); ++iter) {
-    AbcObjectReader *reader = *iter;
+  for (AbcObjectReader *reader : data->reader_manager.all_readers()) {
     reader->decref();
 
     if (reader->refcount() == 0) {
@@ -781,23 +792,28 @@ static ISampleSelector sample_selector_for_time(float time)
   return ISampleSelector(time, ISampleSelector::kFloorIndex);
 }
 
-Mesh *ABC_read_mesh(CacheReader *reader,
-                    Object *ob,
-                    Mesh *existing_mesh,
-                    const float time,
-                    const char **err_str,
-                    const int read_flag,
-                    const char *velocity_name,
-                    const float velocity_scale)
+void ABC_read_geometry(CacheReader *reader,
+                       Object *ob,
+                       GeometrySet &geometry_set,
+                       const ABCReadParams *params,
+                       const char **err_str)
 {
   AbcObjectReader *abc_reader = get_abc_reader(reader, ob, err_str);
   if (abc_reader == nullptr) {
-    return nullptr;
+    return;
   }
 
-  ISampleSelector sample_sel = sample_selector_for_time(time);
-  return abc_reader->read_mesh(
-      existing_mesh, sample_sel, read_flag, velocity_name, velocity_scale, err_str);
+  AttributeSelector attribute_selector(params->mappings);
+  attribute_selector.set_velocity_attribute(params->velocity_name);
+  attribute_selector.set_read_flags(params->read_flags);
+
+  ISampleSelector sample_sel = sample_selector_for_time(params->time);
+  abc_reader->read_geometry(geometry_set,
+                            sample_sel,
+                            &attribute_selector,
+                            params->read_flags,
+                            params->velocity_scale,
+                            err_str);
 }
 
 bool ABC_mesh_topology_changed(

source/blender/io/usd/CMakeLists.txt

@@ -25,6 +25,7 @@ set(INC
   ../../bmesh
   ../../depsgraph
   ../../editors/include
+  ../../functions
   ../../makesdna
   ../../makesrna
   ../../windowmanager

source/blender/io/usd/intern/usd_capi_import.cc

@@ -420,20 +420,20 @@ static USDPrimReader *get_usd_reader(CacheReader *reader, Object * /* ob */, con
   return usd_reader;
 }
 
-struct Mesh *USD_read_mesh(struct CacheReader *reader,
-                           struct Object *ob,
-                           struct Mesh *existing_mesh,
-                           const float time,
-                           const char **err_str,
-                           const int read_flag)
+void USD_read_geometry(CacheReader *reader,
+                       Object *ob,
+                       GeometrySet &geometry_set,
+                       const float time,
+                       const char **err_str,
+                       const int read_flag)
 {
   USDGeomReader *usd_reader = dynamic_cast<USDGeomReader *>(get_usd_reader(reader, ob, err_str));
 
   if (usd_reader == nullptr) {
-    return nullptr;
+    return;
   }
 
-  return usd_reader->read_mesh(existing_mesh, time, read_flag, err_str);
+  return usd_reader->read_geometry(geometry_set, time, read_flag, err_str);
 }
 
 bool USD_mesh_topology_changed(

source/blender/io/usd/intern/usd_reader_curve.cc

@@ -5,8 +5,10 @@
 #include "usd_reader_curve.h"
 
 #include "BKE_curve.h"
+#include "BKE_geometry_set.hh"
 #include "BKE_mesh.h"
 #include "BKE_object.h"
+#include "BKE_spline.hh"
 
 #include "BLI_listbase.h"
 
@@ -161,15 +163,39 @@ void USDCurvesReader::read_curve_sample(Curve *cu, const double motionSampleTime
   }
 }
 
-Mesh *USDCurvesReader::read_mesh(struct Mesh *existing_mesh,
-                                 const double motionSampleTime,
-                                 const int /* read_flag */,
-                                 const char ** /* err_str */)
+static bool topology_changed(CurveEval *curve_eval, const pxr::VtIntArray &usdCounts)
 {
-  if (!curve_prim_) {
-    return existing_mesh;
+  if (!curve_eval) {
+    return true;
   }
 
+  if (curve_eval->splines().size() != usdCounts.size()) {
+    return true;
+  }
+
+  int curve_idx = 0;
+  for (const SplinePtr &spline : curve_eval->splines()) {
+    const int num_in_usd = usdCounts[curve_idx++];
+    const int num_in_blender = spline->positions().size();
+
+    if (num_in_usd != num_in_blender) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+void USDCurvesReader::read_geometry(GeometrySet &geometry_set,
+                                    double motionSampleTime,
+                                    int /* read_flag */,
+                                    const char ** /* err_str */)
+{
+  if (!curve_prim_) {
+    return;
+  }
+
+#if 0
   pxr::UsdAttribute widthsAttr = curve_prim_.GetWidthsAttr();
   pxr::UsdAttribute vertexAttr = curve_prim_.GetCurveVertexCountsAttr();
   pxr::UsdAttribute pointsAttr = curve_prim_.GetPointsAttr();
@@ -177,62 +203,37 @@ Mesh *USDCurvesReader::read_mesh(struct Mesh *existing_mesh,
   pxr::VtIntArray usdCounts;
 
   vertexAttr.Get(&usdCounts, motionSampleTime);
-  int num_subcurves = usdCounts.size();
 
   pxr::VtVec3fArray usdPoints;
   pointsAttr.Get(&usdPoints, motionSampleTime);
 
   int vertex_idx = 0;
   int curve_idx;
-  Curve *curve = static_cast<Curve *>(object_->data);
+  CurveEval *curve_eval = geometry_set.get_curve_for_write();
 
-  const int curve_count = BLI_listbase_count(&curve->nurb);
-  bool same_topology = curve_count == num_subcurves;
-
-  if (same_topology) {
-    Nurb *nurbs = static_cast<Nurb *>(curve->nurb.first);
-    for (curve_idx = 0; nurbs; nurbs = nurbs->next, curve_idx++) {
-      const int num_in_usd = usdCounts[curve_idx];
-      const int num_in_blender = nurbs->pntsu;
-
-      if (num_in_usd != num_in_blender) {
-        same_topology = false;
-        break;
-      }
-    }
-  }
-
-  if (!same_topology) {
+  if (blender::io::usd::topology_changed(curve_eval, usdCounts)) {
+    Curve *curve = static_cast<Curve *>(object_->data);
     BKE_nurbList_free(&curve->nurb);
     read_curve_sample(curve, motionSampleTime);
+
+    std::unique_ptr<CurveEval> new_curve_eval = curve_eval_from_dna_curve(*curve);
+    geometry_set.replace_curve(new_curve_eval.release(), GeometryOwnershipType::Editable);
   }
   else {
-    Nurb *nurbs = static_cast<Nurb *>(curve->nurb.first);
-    for (curve_idx = 0; nurbs; nurbs = nurbs->next, curve_idx++) {
-      const int totpoint = usdCounts[curve_idx];
+    BLI_assert_msg(curve_eval, "curve_eval is null although the topology is the same !");
+    const int curve_count = curve_eval->splines().size();
+    for (curve_idx = 0; curve_idx < curve_count; curve_idx++) {
+      Spline *spline = curve_eval->splines()[curve_idx].get();
 
-      if (nurbs->bp) {
-        BPoint *point = nurbs->bp;
-
-        for (int i = 0; i < totpoint; i++, point++, vertex_idx++) {
-          point->vec[0] = usdPoints[vertex_idx][0];
-          point->vec[1] = usdPoints[vertex_idx][1];
-          point->vec[2] = usdPoints[vertex_idx][2];
-        }
-      }
-      else if (nurbs->bezt) {
-        BezTriple *bezier = nurbs->bezt;
-
-        for (int i = 0; i < totpoint; i++, bezier++, vertex_idx++) {
-          bezier->vec[1][0] = usdPoints[vertex_idx][0];
-          bezier->vec[1][1] = usdPoints[vertex_idx][1];
-          bezier->vec[1][2] = usdPoints[vertex_idx][2];
-        }
+      for (float3 &position : spline->positions()) {
+        position.x = usdPoints[vertex_idx][0];
+        position.y = usdPoints[vertex_idx][0];
+        position.z = usdPoints[vertex_idx][0];
+        vertex_idx++;
       }
     }
   }
-
-  return BKE_mesh_new_nomain_from_curve(object_);
+#endif
 }
 
 }  // namespace blender::io::usd

source/blender/io/usd/intern/usd_reader_curve.h

@@ -35,10 +35,10 @@ class USDCurvesReader : public USDGeomReader {
 
   void read_curve_sample(Curve *cu, double motionSampleTime);
 
-  Mesh *read_mesh(struct Mesh *existing_mesh,
-                  double motionSampleTime,
-                  int read_flag,
-                  const char **err_str) override;
+  void read_geometry(GeometrySet &geometry_set,
+                     double motionSampleTime,
+                     int read_flag,
+                     const char **err_str) override;
 };
 
 }  // namespace blender::io::usd

source/blender/io/usd/intern/usd_reader_geom.h

@@ -5,6 +5,7 @@
 #include "usd.h"
 #include "usd_reader_xform.h"
 
+struct GeometrySet;
 struct Mesh;
 
 namespace blender::io::usd {
@@ -19,10 +20,10 @@ class USDGeomReader : public USDXformReader {
   {
   }
 
-  virtual Mesh *read_mesh(struct Mesh *existing_mesh,
-                          double motionSampleTime,
-                          int read_flag,
-                          const char **err_str) = 0;
+  virtual void read_geometry(GeometrySet &geometry_set,
+                             double motionSampleTime,
+                             int read_flag,
+                             const char **err_str) = 0;
 
   virtual bool topology_changed(Mesh * /* existing_mesh */, double /* motionSampleTime */)
   {

source/blender/io/usd/intern/usd_reader_mesh.cc

@@ -7,6 +7,7 @@
 #include "usd_reader_material.h"
 
 #include "BKE_customdata.h"
+#include "BKE_geometry_set.hh"
 #include "BKE_main.h"
 #include "BKE_material.h"
 #include "BKE_mesh.h"
@@ -866,4 +867,17 @@ Mesh *USDMeshReader::read_mesh(Mesh *existing_mesh,
   return active_mesh;
 }
 
+void USDMeshReader::read_geometry(GeometrySet &geometry_set,
+                                  double motionSampleTime,
+                                  int read_flag,
+                                  const char **err_str)
+{
+  Mesh *existing_mesh = geometry_set.get_mesh_for_write();
+  Mesh *new_mesh = read_mesh(existing_mesh, motionSampleTime, read_flag, err_str);
+
+  if (new_mesh != existing_mesh) {
+    geometry_set.replace_mesh(new_mesh);
+  }
+}
+
 }  // namespace blender::io::usd

source/blender/io/usd/intern/usd_reader_mesh.h

@@ -48,10 +48,10 @@ class USDMeshReader : public USDGeomReader {
   void create_object(Main *bmain, double motionSampleTime) override;
   void read_object_data(Main *bmain, double motionSampleTime) override;
 
-  struct Mesh *read_mesh(struct Mesh *existing_mesh,
-                         double motionSampleTime,
-                         int read_flag,
-                         const char **err_str) override;
+  void read_geometry(GeometrySet &geometry_set,
+                     double motionSampleTime,
+                     int read_flag,
+                     const char **err_str) override;
 
   bool topology_changed(Mesh *existing_mesh, double motionSampleTime) override;
 
@@ -75,6 +75,11 @@ class USDMeshReader : public USDGeomReader {
                         Mesh *mesh,
                         double motionSampleTime,
                         bool new_mesh);
+
+  struct Mesh *read_mesh(struct Mesh *existing_mesh,
+                         double motionSampleTime,
+                         int read_flag,
+                         const char **err_str);
 };
 
 }  // namespace blender::io::usd

source/blender/io/usd/intern/usd_reader_nurbs.cc

@@ -5,8 +5,10 @@
 #include "usd_reader_nurbs.h"
 
 #include "BKE_curve.h"
+#include "BKE_geometry_set.hh"
 #include "BKE_mesh.h"
 #include "BKE_object.h"
+#include "BKE_spline.hh"
 
 #include "BLI_listbase.h"
 
@@ -164,11 +166,35 @@ void USDNurbsReader::read_curve_sample(Curve *cu, const double motionSampleTime)
   }
 }
 
-Mesh *USDNurbsReader::read_mesh(struct Mesh * /* existing_mesh */,
-                                const double motionSampleTime,
-                                const int /* read_flag */,
-                                const char ** /* err_str */)
+static bool topology_changed(CurveEval *curve_eval, const pxr::VtIntArray &usdCounts)
 {
+  if (!curve_eval) {
+    return true;
+  }
+
+  if (curve_eval->splines().size() != usdCounts.size()) {
+    return true;
+  }
+
+  int curve_idx = 0;
+  for (const SplinePtr &spline : curve_eval->splines()) {
+    const int num_in_usd = usdCounts[curve_idx++];
+    const int num_in_blender = spline->positions().size();
+
+    if (num_in_usd != num_in_blender) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+void USDNurbsReader::read_geometry(GeometrySet &geometry_set,
+                                   double motionSampleTime,
+                                   int /* read_flag */,
+                                   const char ** /* err_str */)
+{
+#if 0
   pxr::UsdGeomCurves curve_prim_(prim_);
 
   pxr::UsdAttribute widthsAttr = curve_prim_.GetWidthsAttr();
@@ -178,62 +204,37 @@ Mesh *USDNurbsReader::read_mesh(struct Mesh * /* existing_mesh */,
   pxr::VtIntArray usdCounts;
 
   vertexAttr.Get(&usdCounts, motionSampleTime);
-  int num_subcurves = usdCounts.size();
 
   pxr::VtVec3fArray usdPoints;
   pointsAttr.Get(&usdPoints, motionSampleTime);
 
   int vertex_idx = 0;
   int curve_idx;
-  Curve *curve = static_cast<Curve *>(object_->data);
+  CurveEval *curve_eval = geometry_set.get_curve_for_write();
 
-  const int curve_count = BLI_listbase_count(&curve->nurb);
-  bool same_topology = curve_count == num_subcurves;
-
-  if (same_topology) {
-    Nurb *nurbs = static_cast<Nurb *>(curve->nurb.first);
-    for (curve_idx = 0; nurbs; nurbs = nurbs->next, curve_idx++) {
-      const int num_in_usd = usdCounts[curve_idx];
-      const int num_in_blender = nurbs->pntsu;
-
-      if (num_in_usd != num_in_blender) {
-        same_topology = false;
-        break;
-      }
-    }
-  }
-
-  if (!same_topology) {
+  if (blender::io::usd::topology_changed(curve_eval, usdCounts)) {
+    Curve *curve = static_cast<Curve *>(object_->data);
     BKE_nurbList_free(&curve->nurb);
     read_curve_sample(curve, motionSampleTime);
+
+    std::unique_ptr<CurveEval> new_curve_eval = curve_eval_from_dna_curve(*curve);
+    geometry_set.replace_curve(new_curve_eval.release(), GeometryOwnershipType::Editable);
   }
   else {
-    Nurb *nurbs = static_cast<Nurb *>(curve->nurb.first);
-    for (curve_idx = 0; nurbs; nurbs = nurbs->next, curve_idx++) {
-      const int totpoint = usdCounts[curve_idx];
+    BLI_assert_msg(curve_eval, "curve_eval is null although the topology is the same !");
+    const int curve_count = curve_eval->splines().size();
+    for (curve_idx = 0; curve_idx < curve_count; curve_idx++) {
+      Spline *spline = curve_eval->splines()[curve_idx].get();
 
-      if (nurbs->bp) {
-        BPoint *point = nurbs->bp;
-
-        for (int i = 0; i < totpoint; i++, point++, vertex_idx++) {
-          point->vec[0] = usdPoints[vertex_idx][0];
-          point->vec[1] = usdPoints[vertex_idx][1];
-          point->vec[2] = usdPoints[vertex_idx][2];
-        }
-      }
-      else if (nurbs->bezt) {
-        BezTriple *bezier = nurbs->bezt;
-
-        for (int i = 0; i < totpoint; i++, bezier++, vertex_idx++) {
-          bezier->vec[1][0] = usdPoints[vertex_idx][0];
-          bezier->vec[1][1] = usdPoints[vertex_idx][1];
-          bezier->vec[1][2] = usdPoints[vertex_idx][2];
-        }
+      for (float3 &position : spline->positions()) {
+        position.x = usdPoints[vertex_idx][0];
+        position.y = usdPoints[vertex_idx][0];
+        position.z = usdPoints[vertex_idx][0];
+        vertex_idx++;
       }
     }
   }
-
-  return BKE_mesh_new_nomain_from_curve(object_);
+#endif
 }
 
 }  // namespace blender::io::usd

source/blender/io/usd/intern/usd_reader_nurbs.h

@@ -35,10 +35,10 @@ class USDNurbsReader : public USDGeomReader {
 
   void read_curve_sample(Curve *cu, double motionSampleTime);
 
-  Mesh *read_mesh(struct Mesh *existing_mesh,
-                  double motionSampleTime,
-                  int read_flag,
-                  const char **err_str) override;
+  void read_geometry(GeometrySet &geometry_set,
+                     double motionSampleTime,
+                     int read_flag,
+                     const char **err_str) override;
 };
 
 }  // namespace blender::io::usd

source/blender/io/usd/usd.h

@@ -12,6 +12,8 @@ extern "C" {
 struct CacheArchiveHandle;
 struct CacheFile;
 struct CacheReader;
+struct GeometrySet;
+struct Mesh;
 struct Object;
 struct bContext;
 
@@ -90,13 +92,14 @@ void USD_free_handle(struct CacheArchiveHandle *handle);
 
 void USD_get_transform(struct CacheReader *reader, float r_mat[4][4], float time, float scale);
 
-/* Either modifies current_mesh in-place or constructs a new mesh. */
-struct Mesh *USD_read_mesh(struct CacheReader *reader,
-                           struct Object *ob,
-                           struct Mesh *existing_mesh,
-                           float time,
-                           const char **err_str,
-                           int read_flag);
+#ifdef __cplusplus
+void USD_read_geometry(CacheReader *reader,
+                       Object *ob,
+                       GeometrySet &geometry_set,
+                       const float time,
+                       const char **err_str,
+                       const int read_flag);
+#endif
 
 bool USD_mesh_topology_changed(struct CacheReader *reader,
                                struct Object *ob,

source/blender/makesdna/DNA_cachefile_types.h

@@ -55,6 +55,44 @@ typedef struct CacheFileLayer {
   int _pad;
 } CacheFileLayer;
 
+/* CacheAttributeMapping::mapping */
+enum {
+  /* Default mapping, so we do not make an arbitrary decision as to what is the default. Also used
+   * to mark the mapping as ignored. */
+  CACHEFILE_ATTRIBUTE_MAP_NONE,
+  CACHEFILE_ATTRIBUTE_MAP_TO_UVS,
+  CACHEFILE_ATTRIBUTE_MAP_TO_VERTEX_COLORS,
+  CACHEFILE_ATTRIBUTE_MAP_TO_WEIGHT_GROUPS,
+  CACHEFILE_ATTRIBUTE_MAP_TO_FLOAT2,
+  CACHEFILE_ATTRIBUTE_MAP_TO_FLOAT3,
+  CACHEFILE_ATTRIBUTE_MAP_TO_COLOR,
+};
+
+/* CacheAttributeMapping::domain */
+enum {
+  /* Try to automatically map the attribute to the right domain (default behavior without mapping.)
+   */
+  CACHEFILE_ATTR_MAP_DOMAIN_AUTO,
+  CACHEFILE_ATTR_MAP_DOMAIN_POINT,
+  CACHEFILE_ATTR_MAP_DOMAIN_FACE_CORNER,
+  CACHEFILE_ATTR_MAP_DOMAIN_FACE,
+  CACHEFILE_ATTR_MAP_DOMAIN_CURVE,
+};
+
+/* Custom data mapping for the attributes in the CacheFile. Since there might not be a standard way
+ * of expressing what an attribute should be (e.g. is this float2 attribute a UV map?), and since
+ * some software might write multi-dimensionnal data as arrays of 1D element (although the size of
+ * the array will be N-time its expected size were it written as N-D data), we delegate to the user
+ * the task of telling us what is supposed to be what through these mappings. */
+typedef struct CacheAttributeMapping {
+  struct CacheAttributeMapping *next, *prev;
+
+  char name[64];
+  char mapping;
+  char domain;
+  char _pad[6];
+} CacheAttributeMapping;
+
 /* CacheFile::velocity_unit
  * Determines what temporal unit is used to interpret velocity vectors for motion blur effects. */
 enum {
@@ -85,7 +123,8 @@ typedef struct CacheFile {
   /** The frame offset to subtract. */
   float frame_offset;
 
-  char _pad[4];
+  /** Index of the currently selected attribute mapping in the UI, starts at 1 */
+  int active_attribute_mapping;
 
   /** Animation flag. */
   short flag;
@@ -116,6 +155,8 @@ typedef struct CacheFile {
   /* Name of the velocity property in the archive. */
   char velocity_name[64];
 
+  ListBase attribute_mappings;
+
   /* Runtime */
   struct CacheArchiveHandle *handle;
   char handle_filepath[1024];

source/blender/makesrna/RNA_access.h

@@ -92,6 +92,7 @@ extern StructRNA RNA_ByteColorAttribute;
 extern StructRNA RNA_ByteColorAttributeValue;
 extern StructRNA RNA_ByteIntAttribute;
 extern StructRNA RNA_ByteIntAttributeValue;
+extern StructRNA RNA_CacheAttributeMapping;
 extern StructRNA RNA_CacheFile;
 extern StructRNA RNA_CacheFileLayer;
 extern StructRNA RNA_Camera;

source/blender/makesrna/intern/rna_cachefile.c

@@ -47,6 +47,16 @@ static void rna_CacheFileLayer_update(Main *UNUSED(bmain), Scene *UNUSED(scene),
   WM_main_add_notifier(NC_OBJECT | ND_DRAW, NULL);
 }
 
+static void rna_CacheFile_attribute_mapping_update(Main *UNUSED(bmain),
+                                                   Scene *UNUSED(scene),
+                                                   PointerRNA *ptr)
+{
+  CacheFile *cache_file = (CacheFile *)ptr->owner_id;
+
+  DEG_id_tag_update(&cache_file->id, ID_RECALC_COPY_ON_WRITE);
+  WM_main_add_notifier(NC_OBJECT | ND_DRAW, NULL);
+}
+
 static void rna_CacheFile_dependency_update(Main *bmain, Scene *scene, PointerRNA *ptr)
 {
   rna_CacheFile_update(bmain, scene, ptr);
@@ -144,6 +154,87 @@ static void rna_CacheFile_layer_remove(CacheFile *cache_file, bContext *C, Point
   WM_main_add_notifier(NC_OBJECT | ND_DRAW, NULL);
 }
 
+static CacheAttributeMapping *rna_CacheFile_attribute_mapping_new(CacheFile *cache_file,
+                                                                  bContext *C,
+                                                                  ReportList *reports,
+                                                                  const char *name,
+                                                                  const int mapping_type,
+                                                                  const int domain)
+{
+  CacheAttributeMapping *mapping = BKE_cachefile_add_attribute_mapping(
+      cache_file, name, mapping_type, domain);
+  if (mapping == NULL) {
+    BKE_reportf(reports,
+                RPT_ERROR,
+                "Cannot add an attribute mapping to CacheFile '%s'",
+                cache_file->id.name + 2);
+    return NULL;
+  }
+
+  Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
+  BKE_cachefile_reload(depsgraph, cache_file);
+  WM_main_add_notifier(NC_OBJECT | ND_DRAW, NULL);
+  return mapping;
+}
+
+static void rna_CacheFile_attribute_mapping_remove(CacheFile *cache_file,
+                                                   bContext *C,
+                                                   PointerRNA *mapping_ptr)
+{
+  CacheAttributeMapping *mapping = mapping_ptr->data;
+  BKE_cachefile_remove_attribute_mapping(cache_file, mapping);
+  Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
+  BKE_cachefile_reload(depsgraph, cache_file);
+  WM_main_add_notifier(NC_OBJECT | ND_DRAW, NULL);
+}
+
+static PointerRNA rna_CacheFile_active_attribute_mapping_get(PointerRNA *ptr)
+{
+  CacheFile *cache_file = (CacheFile *)ptr->owner_id;
+  return rna_pointer_inherit_refine(
+      ptr, &RNA_CacheAttributeMapping, BKE_cachefile_get_active_attribute_mapping(cache_file));
+}
+
+static void rna_CacheFile_active_attribute_mapping_set(PointerRNA *ptr,
+                                                       PointerRNA value,
+                                                       struct ReportList *reports)
+{
+  CacheFile *cache_file = (CacheFile *)ptr->owner_id;
+  int index = BLI_findindex(&cache_file->attribute_mappings, value.data);
+  if (index == -1) {
+    BKE_reportf(reports,
+                RPT_ERROR,
+                "Attribute mapping '%s' not found in object '%s'",
+                ((CacheAttributeMapping *)value.data)->name,
+                cache_file->id.name + 2);
+    cache_file->active_attribute_mapping = 0;
+    return;
+  }
+
+  cache_file->active_attribute_mapping = index + 1;
+}
+
+static int rna_CacheFile_active_attribute_mapping_index_get(PointerRNA *ptr)
+{
+  CacheFile *cache_file = (CacheFile *)ptr->owner_id;
+  return cache_file->active_attribute_mapping - 1;
+}
+
+static void rna_CacheFile_active_attribute_mapping_index_set(PointerRNA *ptr, int value)
+{
+  CacheFile *cache_file = (CacheFile *)ptr->owner_id;
+  cache_file->active_attribute_mapping = value + 1;
+}
+
+static void rna_CacheFile_active_attribute_mapping_index_range(
+    PointerRNA *ptr, int *min, int *max, int *UNUSED(softmin), int *UNUSED(softmax))
+{
+  CacheFile *cache_file = (CacheFile *)ptr->owner_id;
+
+  *min = 0;
+  *max = max_ii(0, BLI_listbase_count(&cache_file->attribute_mappings) - 1);
+}
+
 #else
 
 /* cachefile.object_paths */
@@ -163,6 +254,148 @@ static void rna_def_alembic_object_path(BlenderRNA *brna)
   RNA_define_lib_overridable(false);
 }
 
+static const EnumPropertyItem rna_enum_cache_attribute_mapping_items[] = {
+    {CACHEFILE_ATTRIBUTE_MAP_NONE, "MAP_NONE", 0, "None", ""},
+    {CACHEFILE_ATTRIBUTE_MAP_TO_UVS,
+     "MAP_TO_UVS",
+     0,
+     "UVs",
+     "Read the attribute as a UV map of the same name"},
+    {CACHEFILE_ATTRIBUTE_MAP_TO_VERTEX_COLORS,
+     "MAP_TO_VERTEX_COLORS",
+     0,
+     "Vertex Colors",
+     "Read the attribute as a vertex color layer of the same name"},
+    {CACHEFILE_ATTRIBUTE_MAP_TO_WEIGHT_GROUPS,
+     "MAP_TO_WEIGHT_GROUPS",
+     0,
+     "Weight Group",
+     "Read the attribute as a weight group channel of the same name"},
+    {CACHEFILE_ATTRIBUTE_MAP_TO_FLOAT2,
+     "MAP_TO_FLOAT2",
+     0,
+     "2D Vector",
+     "Interpret the attribute's data as generic 2D vectors"},
+    {CACHEFILE_ATTRIBUTE_MAP_TO_FLOAT3,
+     "MAP_TO_FLOAT3",
+     0,
+     "3D Vector",
+     "Interpret the attribute's data as generic 3D vectors"},
+    {CACHEFILE_ATTRIBUTE_MAP_TO_COLOR,
+     "MAP_TO_COLOR",
+     0,
+     "Color",
+     "Interpret the attribute's data as colors (RGBA)"},
+    {0, NULL, 0, NULL, NULL},
+};
+
+static const EnumPropertyItem rna_enum_cache_attribute_domain_items[] = {
+    {CACHEFILE_ATTR_MAP_DOMAIN_AUTO,
+     "AUTO",
+     0,
+     "Automatic",
+     "Try to automatically determine the domain of the attribute"},
+    {CACHEFILE_ATTR_MAP_DOMAIN_POINT,
+     "POINT",
+     0,
+     "Point",
+     "The attribute is defined for each point"},
+    {CACHEFILE_ATTR_MAP_DOMAIN_FACE_CORNER,
+     "FACE_CORNER",
+     0,
+     "Face Corner",
+     "The attribute is defined for each face corner"},
+    {CACHEFILE_ATTR_MAP_DOMAIN_FACE, "FACE", 0, "Face", "The attribute is defined for each face"},
+    {CACHEFILE_ATTR_MAP_DOMAIN_CURVE,
+     "CURVE",
+     0,
+     "Curve",
+     "The attribute is defined for each curve"},
+    {0, NULL, 0, NULL, NULL},
+};
+
+static void rna_def_cachefile_attribute_mapping(BlenderRNA *brna)
+{
+  StructRNA *srna = RNA_def_struct(brna, "CacheAttributeMapping", NULL);
+  RNA_def_struct_sdna(srna, "CacheAttributeMapping");
+  RNA_def_struct_ui_text(
+      srna,
+      "Cache Attribute Mapping",
+      "Attribute Mappin of the cache, used to define how to interpret certain attributes");
+
+  PropertyRNA *prop = RNA_def_property(srna, "name", PROP_STRING, PROP_NONE);
+  RNA_def_property_ui_text(prop, "Name", "Name of the attribute to map");
+  RNA_def_property_update(prop, 0, "rna_CacheFile_attribute_mapping_update");
+
+  prop = RNA_def_property(srna, "mapping", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_items(prop, rna_enum_cache_attribute_mapping_items);
+  RNA_def_property_update(prop, 0, "rna_CacheFile_attribute_mapping_update");
+  RNA_def_property_ui_text(prop, "Data Type", "Define the data type of the attribute");
+
+  prop = RNA_def_property(srna, "domain", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_items(prop, rna_enum_cache_attribute_domain_items);
+  RNA_def_property_update(prop, 0, "rna_CacheFile_attribute_mapping_update");
+  RNA_def_property_ui_text(prop, "Domain", "Define the domain on which the attribute is written");
+}
+
+static void rna_def_cachefile_attribute_mappings(BlenderRNA *brna, PropertyRNA *cprop)
+{
+  RNA_def_property_srna(cprop, "CacheAttributeMappings");
+  StructRNA *srna = RNA_def_struct(brna, "CacheAttributeMappings", NULL);
+  RNA_def_struct_sdna(srna, "CacheFile");
+  RNA_def_struct_ui_text(
+      srna, "Cache Attribute Mappings", "Collection of cache attribute mappings");
+
+  PropertyRNA *prop = RNA_def_property(srna, "active", PROP_POINTER, PROP_NONE);
+  RNA_def_property_struct_type(prop, "CacheAttributeMapping");
+  RNA_def_property_pointer_funcs(prop,
+                                 "rna_CacheFile_active_attribute_mapping_get",
+                                 "rna_CacheFile_active_attribute_mapping_set",
+                                 NULL,
+                                 NULL);
+  RNA_def_property_flag(prop, PROP_EDITABLE);
+  RNA_def_property_ui_text(
+      prop, "Active Attribute Mapping", "Active attribute mapping of the CacheFile");
+  RNA_def_property_ui_text(
+      prop, "Active Attribute Mapping Index", "Active index in attribute mappings array");
+
+  FunctionRNA *func;
+  PropertyRNA *parm;
+
+  /* Add a mapping. */
+  func = RNA_def_function(srna, "new", "rna_CacheFile_attribute_mapping_new");
+  RNA_def_function_flag(func, FUNC_USE_REPORTS | FUNC_USE_CONTEXT);
+  RNA_def_function_ui_description(func, "Add a new attribute mapping");
+  /* Optional parameters. */
+  parm = RNA_def_string(func, "name", "Name", 64, "Name", "Name of the attribute to remap");
+  parm = RNA_def_enum(func,
+                      "mapping_type",
+                      rna_enum_cache_attribute_mapping_items,
+                      CACHEFILE_ATTRIBUTE_MAP_NONE,
+                      "Mapping Type",
+                      "Type of the mapping");
+  parm = RNA_def_enum(func,
+                      "domain",
+                      rna_enum_cache_attribute_domain_items,
+                      CACHEFILE_ATTR_MAP_DOMAIN_AUTO,
+                      "Domain",
+                      "Original domain of the attribute to remap");
+  /* Return type. */
+  parm = RNA_def_pointer(
+      func, "mapping", "CacheAttributeMapping", "", "Newly created attribute mapping");
+  RNA_def_function_return(func, parm);
+
+  /* Remove a mapping. */
+  func = RNA_def_function(srna, "remove", "rna_CacheFile_attribute_mapping_remove");
+  RNA_def_function_flag(func, FUNC_USE_CONTEXT);
+  RNA_def_function_ui_description(func,
+                                  "Remove an existing attribute mapping from the cache file");
+  parm = RNA_def_pointer(
+      func, "mapping", "CacheAttributeMapping", "", "Attribute mapping to remove");
+  RNA_def_parameter_flags(parm, PROP_NEVER_NULL, PARM_REQUIRED | PARM_RNAPTR);
+  RNA_def_parameter_clear_flags(parm, PROP_THICK_WRAP, 0);
+}
+
 /* cachefile.object_paths */
 static void rna_def_cachefile_object_paths(BlenderRNA *brna, PropertyRNA *cprop)
 {
@@ -255,6 +488,18 @@ static void rna_def_cachefile(BlenderRNA *brna)
       "Alembic data themselves if possible");
   RNA_def_property_update(prop, 0, "rna_CacheFile_dependency_update");
 
+  static const EnumPropertyItem cache_file_type_items[] = {
+      {CACHE_FILE_TYPE_INVALID, "INVALID", 0, "Invalid", ""},
+      {CACHEFILE_TYPE_ALEMBIC, "ALEMBIC", 0, "Alembic", ""},
+      {CACHEFILE_TYPE_USD, "USD", 0, "USD", ""},
+      {0, NULL, 0, NULL, NULL},
+  };
+
+  prop = RNA_def_property(srna, "type", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_items(prop, cache_file_type_items);
+  RNA_def_property_ui_text(prop, "Type", "Type of the file used for storing data");
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+
   /* ----------------- For Scene time ------------------- */
 
   prop = RNA_def_property(srna, "override_frame", PROP_BOOLEAN, PROP_NONE);
@@ -384,6 +629,23 @@ static void rna_def_cachefile(BlenderRNA *brna)
                              "rna_CacheFile_active_layer_index_set",
                              "rna_CacheFile_active_layer_index_range");
 
+  /* ----------------- Attribute Mappings ----------------- */
+
+  prop = RNA_def_property(srna, "attribute_mappings", PROP_COLLECTION, PROP_NONE);
+  RNA_def_property_collection_sdna(prop, NULL, "attribute_mappings", NULL);
+  RNA_def_property_struct_type(prop, "CacheAttributeMapping");
+  RNA_def_property_override_clear_flag(prop, PROPOVERRIDE_OVERRIDABLE_LIBRARY);
+  RNA_def_property_ui_text(prop, "Cache Attribute Mappings", "Attribute mappings of the cache");
+  rna_def_cachefile_attribute_mappings(brna, prop);
+
+  prop = RNA_def_property(srna, "active_attribute_mapping_index", PROP_INT, PROP_UNSIGNED);
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_int_sdna(prop, NULL, "active_attribute_mapping");
+  RNA_def_property_int_funcs(prop,
+                             "rna_CacheFile_active_attribute_mapping_index_get",
+                             "rna_CacheFile_active_attribute_mapping_index_set",
+                             "rna_CacheFile_active_attribute_mapping_index_range");
+
   RNA_define_lib_overridable(false);
 
   rna_def_cachefile_object_paths(brna, prop);
@@ -396,6 +658,7 @@ void RNA_def_cachefile(BlenderRNA *brna)
   rna_def_cachefile(brna);
   rna_def_alembic_object_path(brna);
   rna_def_cachefile_layer(brna);
+  rna_def_cachefile_attribute_mapping(brna);
 }
 
 #endif

source/blender/modifiers/CMakeLists.txt

@@ -59,7 +59,7 @@ set(SRC
   intern/MOD_meshcache_pc2.c
   intern/MOD_meshcache_util.c
   intern/MOD_meshdeform.c
-  intern/MOD_meshsequencecache.c
+  intern/MOD_meshsequencecache.cc
   intern/MOD_mirror.c
   intern/MOD_multires.c
   intern/MOD_nodes.cc

source/blender/modifiers/intern/MOD_meshsequencecache.cc

@@ -25,11 +25,14 @@
 
 #include "BKE_cachefile.h"
 #include "BKE_context.h"
+#include "BKE_curve_to_mesh.hh"
+#include "BKE_geometry_set.hh"
 #include "BKE_lib_query.h"
 #include "BKE_mesh.h"
 #include "BKE_object.h"
 #include "BKE_scene.h"
 #include "BKE_screen.h"
+#include "BKE_spline.hh"
 
 #include "UI_interface.h"
 #include "UI_resources.h"
@@ -79,7 +82,7 @@ static void copyData(const ModifierData *md, ModifierData *target, const int fla
 
   BKE_modifier_copydata_generic(md, target, flag);
 
-  tmcmd->reader = NULL;
+  tmcmd->reader = nullptr;
   tmcmd->reader_object_path[0] = '\0';
 }
 
@@ -100,7 +103,41 @@ static bool isDisabled(const struct Scene *UNUSED(scene),
   MeshSeqCacheModifierData *mcmd = (MeshSeqCacheModifierData *)md;
 
   /* leave it up to the modifier to check the file is valid on calculation */
-  return (mcmd->cache_file == NULL) || (mcmd->object_path[0] == '\0');
+  return (mcmd->cache_file == nullptr) || (mcmd->object_path[0] == '\0');
+}
+
+/* If this invocation is for the ORCO mesh, and the mesh hasn't changed topology, we
+ * must return the mesh as-is instead of deforming it. */
+static bool need_orco_mesh(MeshSeqCacheModifierData *mcmd,
+                           const ModifierEvalContext *ctx,
+                           Mesh *mesh,
+                           float time,
+                           const char **err_str)
+{
+  CacheFile *cache_file = mcmd->cache_file;
+
+  if (ctx->flag & MOD_APPLY_ORCO) {
+    switch (cache_file->type) {
+      case CACHEFILE_TYPE_ALEMBIC:
+#ifdef WITH_ALEMBIC
+        if (!ABC_mesh_topology_changed(mcmd->reader, ctx->object, mesh, time, err_str)) {
+          return true;
+        }
+#endif
+        break;
+      case CACHEFILE_TYPE_USD:
+#ifdef WITH_USD
+        if (!USD_mesh_topology_changed(mcmd->reader, ctx->object, mesh, time, err_str)) {
+          return true;
+        }
+#endif
+        break;
+      case CACHE_FILE_TYPE_INVALID:
+        break;
+    }
+  }
+
+  return false;
 }
 
 static Mesh *generate_bounding_box_mesh(Object *object, Mesh *org_mesh)
@@ -141,20 +178,103 @@ static Mesh *generate_bounding_box_mesh(Object *object, Mesh *org_mesh)
   return result;
 }
 
+static void modifyGeometry(ModifierData *md,
+                           const ModifierEvalContext *ctx,
+                           GeometrySet &geometry_set)
+{
+#ifdef WITH_ALEMBIC
+  MeshSeqCacheModifierData *mcmd = reinterpret_cast<MeshSeqCacheModifierData *>(md);
+
+  Scene *scene = DEG_get_evaluated_scene(ctx->depsgraph);
+  CacheFile *cache_file = mcmd->cache_file;
+  const float frame = DEG_get_ctime(ctx->depsgraph);
+  const float time = BKE_cachefile_time_offset(cache_file, frame, FPS);
+  const char *err_str = nullptr;
+
+  if (!mcmd->reader || !STREQ(mcmd->reader_object_path, mcmd->object_path)) {
+    STRNCPY(mcmd->reader_object_path, mcmd->object_path);
+    BKE_cachefile_reader_open(cache_file, &mcmd->reader, ctx->object, mcmd->object_path);
+    if (!mcmd->reader) {
+      BKE_modifier_set_error(
+          ctx->object, md, "Could not create Alembic reader for file %s", cache_file->filepath);
+      return;
+    }
+  }
+
+  if (geometry_set.has_mesh()) {
+    Mesh *mesh = geometry_set.get_mesh_for_write();
+    if (need_orco_mesh(mcmd, ctx, mesh, time, &err_str)) {
+      return;
+    }
+  }
+
+  /* Do not process data if using a render procedural, return a box instead for displaying in the
+   * viewport. */
+  if (BKE_cache_file_uses_render_procedural(cache_file, scene, DEG_get_mode(ctx->depsgraph))) {
+    Mesh *org_mesh = nullptr;
+    if (geometry_set.has_mesh()) {
+      org_mesh = geometry_set.get_mesh_for_write();
+    }
+
+    Mesh *bbox = generate_bounding_box_mesh(ctx->object, org_mesh);
+    geometry_set = GeometrySet::create_with_mesh(bbox, GeometryOwnershipType::Editable);
+    return;
+  }
+
+  /* Time (in frames or seconds) between two velocity samples. Automatically computed to
+   * scale the velocity vectors at render time for generating proper motion blur data. */
+  float velocity_scale = mcmd->velocity_scale;
+  if (mcmd->cache_file->velocity_unit == CACHEFILE_VELOCITY_UNIT_FRAME) {
+    velocity_scale *= FPS;
+  }
+
+  switch (cache_file->type) {
+    default: {
+      break;
+    }
+#  ifdef WITH_ALEMBIC
+    case CACHEFILE_TYPE_ALEMBIC: {
+      ABCReadParams params;
+      params.time = time;
+      params.read_flags = mcmd->read_flag;
+      params.velocity_name = mcmd->cache_file->velocity_name;
+      params.velocity_scale = velocity_scale;
+      params.mappings = &mcmd->cache_file->attribute_mappings;
+      ABC_read_geometry(mcmd->reader, ctx->object, geometry_set, &params, &err_str);
+      break;
+    }
+#  endif
+#  ifdef WITH_USD
+    case CACHEFILE_TYPE_USD: {
+      USD_read_geometry(mcmd->reader, ctx->object, geometry_set, time, &err_str, mcmd->read_flag);
+    }
+#  endif
+  }
+
+  if (err_str) {
+    BKE_modifier_set_error(ctx->object, md, "%s", err_str);
+  }
+
+#else
+  UNUSED_VARS(ctx, md, geometry_set);
+  return;
+#endif
+}
+
 static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *mesh)
 {
 #if defined(WITH_USD) || defined(WITH_ALEMBIC)
   MeshSeqCacheModifierData *mcmd = (MeshSeqCacheModifierData *)md;
 
   /* Only used to check whether we are operating on org data or not... */
-  Mesh *me = (ctx->object->type == OB_MESH) ? ctx->object->data : NULL;
+  Mesh *me = (ctx->object->type == OB_MESH) ? static_cast<Mesh *>(ctx->object->data) : nullptr;
   Mesh *org_mesh = mesh;
 
   Scene *scene = DEG_get_evaluated_scene(ctx->depsgraph);
   CacheFile *cache_file = mcmd->cache_file;
   const float frame = DEG_get_ctime(ctx->depsgraph);
   const float time = BKE_cachefile_time_offset(cache_file, frame, FPS);
-  const char *err_str = NULL;
+  const char *err_str = nullptr;
 
   if (!mcmd->reader || !STREQ(mcmd->reader_object_path, mcmd->object_path)) {
     STRNCPY(mcmd->reader_object_path, mcmd->object_path);
@@ -172,30 +292,11 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
     return generate_bounding_box_mesh(ctx->object, org_mesh);
   }
 
-  /* If this invocation is for the ORCO mesh, and the mesh hasn't changed topology, we
-   * must return the mesh as-is instead of deforming it. */
-  if (ctx->flag & MOD_APPLY_ORCO) {
-    switch (cache_file->type) {
-      case CACHEFILE_TYPE_ALEMBIC:
-#  ifdef WITH_ALEMBIC
-        if (!ABC_mesh_topology_changed(mcmd->reader, ctx->object, mesh, time, &err_str)) {
-          return mesh;
-        }
-#  endif
-        break;
-      case CACHEFILE_TYPE_USD:
-#  ifdef WITH_USD
-        if (!USD_mesh_topology_changed(mcmd->reader, ctx->object, mesh, time, &err_str)) {
-          return mesh;
-        }
-#  endif
-        break;
-      case CACHE_FILE_TYPE_INVALID:
-        break;
-    }
+  if (need_orco_mesh(mcmd, ctx, mesh, time, &err_str)) {
+    return mesh;
   }
 
-  if (me != NULL) {
+  if (me != nullptr) {
     MVert *mvert = mesh->mvert;
     MEdge *medge = mesh->medge;
     MPoly *mpoly = mesh->mpoly;
@@ -204,53 +305,46 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
      * flags) and duplicate those too. */
     if ((me->mvert == mvert) || (me->medge == medge) || (me->mpoly == mpoly)) {
       /* We need to duplicate data here, otherwise we'll modify org mesh, see T51701. */
-      mesh = (Mesh *)BKE_id_copy_ex(NULL,
+      mesh = (Mesh *)BKE_id_copy_ex(nullptr,
                                     &mesh->id,
-                                    NULL,
+                                    nullptr,
                                     LIB_ID_CREATE_NO_MAIN | LIB_ID_CREATE_NO_USER_REFCOUNT |
                                         LIB_ID_CREATE_NO_DEG_TAG | LIB_ID_COPY_NO_PREVIEW);
     }
   }
 
-  Mesh *result = NULL;
+  Mesh *result = nullptr;
 
-  switch (cache_file->type) {
-    case CACHEFILE_TYPE_ALEMBIC: {
-#  ifdef WITH_ALEMBIC
-      /* Time (in frames or seconds) between two velocity samples. Automatically computed to
-       * scale the velocity vectors at render time for generating proper motion blur data. */
-      float velocity_scale = mcmd->velocity_scale;
-      if (mcmd->cache_file->velocity_unit == CACHEFILE_VELOCITY_UNIT_FRAME) {
-        velocity_scale *= FPS;
-      }
+  GeometrySet geometry_set;
 
-      result = ABC_read_mesh(mcmd->reader,
-                             ctx->object,
-                             mesh,
-                             time,
-                             &err_str,
-                             mcmd->read_flag,
-                             mcmd->cache_file->velocity_name,
-                             velocity_scale);
-#  endif
-      break;
+  /*  if (ctx->object->type == OB_CURVES_LEGACY) {
+      std::unique_ptr<CurveEval> curve_eval = curve_eval_from_dna_curve(
+          *static_cast<Curve *>(ctx->object->data));
+      geometry_set = GeometrySet::create_with_curve(curve_eval.release(),
+                                                    GeometryOwnershipType::Editable);
     }
-    case CACHEFILE_TYPE_USD:
-#  ifdef WITH_USD
-      result = USD_read_mesh(
-          mcmd->reader, ctx->object, mesh, time * FPS, &err_str, mcmd->read_flag);
-#  endif
-      break;
-    case CACHE_FILE_TYPE_INVALID:
-      break;
+    else */
+  {
+    geometry_set = GeometrySet::create_with_mesh(mesh, GeometryOwnershipType::Editable);
   }
 
-  if (err_str) {
-    BKE_modifier_set_error(ctx->object, md, "%s", err_str);
+  modifyGeometry(md, ctx, geometry_set);
+
+  /*  if (ctx->object->type == OB_CURVES_LEGACY) {
+      CurveEval *curve_eval = geometry_set.get_component_for_write<CurveComponent>().release();
+
+      if (curve_eval) {
+        result = blender::bke::curve_to_wire_mesh(*curve_eval);
+        delete curve_eval;
+      }
+    }
+    else */
+  {
+    result = geometry_set.get_component_for_write<MeshComponent>().release();
   }
 
-  if (!ELEM(result, NULL, mesh) && (mesh != org_mesh)) {
-    BKE_id_free(NULL, mesh);
+  if (!ELEM(result, nullptr, mesh) && (mesh != org_mesh)) {
+    BKE_id_free(nullptr, mesh);
     mesh = org_mesh;
   }
 
@@ -261,6 +355,13 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
 #endif
 }
 
+static void modifyGeometrySet(ModifierData *md,
+                              const ModifierEvalContext *ctx,
+                              GeometrySet *geometry_set)
+{
+  modifyGeometry(md, ctx, *geometry_set);
+}
+
 static bool dependsOnTime(Scene *scene, ModifierData *md, const int dag_eval_mode)
 {
 #if defined(WITH_USD) || defined(WITH_ALEMBIC)
@@ -285,7 +386,7 @@ static void updateDepsgraph(ModifierData *md, const ModifierUpdateDepsgraphConte
 {
   MeshSeqCacheModifierData *mcmd = (MeshSeqCacheModifierData *)md;
 
-  if (mcmd->cache_file != NULL) {
+  if (mcmd->cache_file != nullptr) {
     DEG_add_object_cache_relation(
         ctx->node, mcmd->cache_file, DEG_OB_COMP_CACHE, "Mesh Cache File");
   }
@@ -306,12 +407,13 @@ static void panel_draw(const bContext *C, Panel *panel)
   uiTemplateCacheFile(layout, C, ptr, "cache_file");
 
   if (has_cache_file) {
-    uiItemPointerR(layout, ptr, "object_path", &cache_file_ptr, "object_paths", NULL, ICON_NONE);
+    uiItemPointerR(
+        layout, ptr, "object_path", &cache_file_ptr, "object_paths", nullptr, ICON_NONE);
   }
 
   if (RNA_enum_get(&ob_ptr, "type") == OB_MESH) {
-    uiItemR(layout, ptr, "read_data", UI_ITEM_R_EXPAND, NULL, ICON_NONE);
-    uiItemR(layout, ptr, "use_vertex_interpolation", 0, NULL, ICON_NONE);
+    uiItemR(layout, ptr, "read_data", UI_ITEM_R_EXPAND, nullptr, ICON_NONE);
+    uiItemR(layout, ptr, "use_vertex_interpolation", 0, nullptr, ICON_NONE);
   }
 
   modifier_panel_end(layout, ptr);
@@ -331,10 +433,42 @@ static void velocity_panel_draw(const bContext *UNUSED(C), Panel *panel)
 
   uiLayoutSetPropSep(layout, true);
   uiTemplateCacheFileVelocity(layout, &fileptr);
-  uiItemR(layout, ptr, "velocity_scale", 0, NULL, ICON_NONE);
+  uiItemR(layout, ptr, "velocity_scale", 0, nullptr, ICON_NONE);
 }
 
-static void time_panel_draw(const bContext *UNUSED(C), Panel *panel)
+static void attribute_remapping_panel_draw(const bContext *C, Panel *panel)
+{
+  uiLayout *layout = panel->layout;
+
+  PointerRNA ob_ptr;
+  PointerRNA *ptr = modifier_panel_get_property_pointers(panel, &ob_ptr);
+
+  PointerRNA fileptr;
+  if (!uiTemplateCacheFilePointer(ptr, "cache_file", &fileptr)) {
+    return;
+  }
+
+  uiLayoutSetPropSep(layout, true);
+  uiTemplateCacheFileAttributeRemapping(layout, C, &fileptr);
+}
+
+static void override_layers_panel_draw(const bContext *C, Panel *panel)
+{
+  uiLayout *layout = panel->layout;
+
+  PointerRNA ob_ptr;
+  PointerRNA *ptr = modifier_panel_get_property_pointers(panel, &ob_ptr);
+
+  PointerRNA fileptr;
+  if (!uiTemplateCacheFilePointer(ptr, "cache_file", &fileptr)) {
+    return;
+  }
+
+  uiLayoutSetPropSep(layout, true);
+  uiTemplateCacheFileLayers(layout, C, &fileptr);
+}
+
+static void time_settings_panel_draw(const bContext *UNUSED(C), Panel *panel)
 {
   uiLayout *layout = panel->layout;
 
@@ -366,47 +500,42 @@ static void render_procedural_panel_draw(const bContext *C, Panel *panel)
   uiTemplateCacheFileProcedural(layout, C, &fileptr);
 }
 
-static void override_layers_panel_draw(const bContext *C, Panel *panel)
-{
-  uiLayout *layout = panel->layout;
-
-  PointerRNA ob_ptr;
-  PointerRNA *ptr = modifier_panel_get_property_pointers(panel, &ob_ptr);
-
-  PointerRNA fileptr;
-  if (!uiTemplateCacheFilePointer(ptr, "cache_file", &fileptr)) {
-    return;
-  }
-
-  uiLayoutSetPropSep(layout, true);
-  uiTemplateCacheFileLayers(layout, C, &fileptr);
-}
-
 static void panelRegister(ARegionType *region_type)
 {
   PanelType *panel_type = modifier_panel_register(
       region_type, eModifierType_MeshSequenceCache, panel_draw);
-  modifier_subpanel_register(region_type, "time", "Time", NULL, time_panel_draw, panel_type);
+  modifier_subpanel_register(region_type,
+                             "time_settings",
+                             "Time Settings",
+                             nullptr,
+                             time_settings_panel_draw,
+                             panel_type);
   modifier_subpanel_register(region_type,
                              "render_procedural",
                              "Render Procedural",
-                             NULL,
+                             nullptr,
                              render_procedural_panel_draw,
                              panel_type);
-  modifier_subpanel_register(
-      region_type, "velocity", "Velocity", NULL, velocity_panel_draw, panel_type);
   modifier_subpanel_register(region_type,
                              "override_layers",
                              "Override Layers",
-                             NULL,
+                             nullptr,
                              override_layers_panel_draw,
                              panel_type);
+  modifier_subpanel_register(
+      region_type, "velocity", "Velocity", nullptr, velocity_panel_draw, panel_type);
+  modifier_subpanel_register(region_type,
+                             "attribute_remapping",
+                             "Attribute Remapping",
+                             nullptr,
+                             attribute_remapping_panel_draw,
+                             panel_type);
 }
 
 static void blendRead(BlendDataReader *UNUSED(reader), ModifierData *md)
 {
   MeshSeqCacheModifierData *msmcd = (MeshSeqCacheModifierData *)md;
-  msmcd->reader = NULL;
+  msmcd->reader = nullptr;
   msmcd->reader_object_path[0] = '\0';
 }
 
@@ -416,29 +545,30 @@ ModifierTypeInfo modifierType_MeshSequenceCache = {
     /* structSize */ sizeof(MeshSeqCacheModifierData),
     /* srna */ &RNA_MeshSequenceCacheModifier,
     /* type */ eModifierTypeType_Constructive,
-    /* flags */ eModifierTypeFlag_AcceptsMesh | eModifierTypeFlag_AcceptsCVs,
+    /* flags */
+    static_cast<ModifierTypeFlag>(eModifierTypeFlag_AcceptsMesh | eModifierTypeFlag_AcceptsCVs),
     /* icon */ ICON_MOD_MESHDEFORM, /* TODO: Use correct icon. */
 
     /* copyData */ copyData,
 
-    /* deformVerts */ NULL,
-    /* deformMatrices */ NULL,
-    /* deformVertsEM */ NULL,
-    /* deformMatricesEM */ NULL,
+    /* deformVerts */ nullptr,
+    /* deformMatrices */ nullptr,
+    /* deformVertsEM */ nullptr,
+    /* deformMatricesEM */ nullptr,
     /* modifyMesh */ modifyMesh,
-    /* modifyGeometrySet */ NULL,
+    /* modifyGeometrySet */ modifyGeometrySet,
 
     /* initData */ initData,
-    /* requiredDataMask */ NULL,
+    /* requiredDataMask */ nullptr,
     /* freeData */ freeData,
     /* isDisabled */ isDisabled,
     /* updateDepsgraph */ updateDepsgraph,
     /* dependsOnTime */ dependsOnTime,
-    /* dependsOnNormals */ NULL,
+    /* dependsOnNormals */ nullptr,
     /* foreachIDLink */ foreachIDLink,
-    /* foreachTexLink */ NULL,
-    /* freeRuntimeData */ NULL,
+    /* foreachTexLink */ nullptr,
+    /* freeRuntimeData */ nullptr,
     /* panelRegister */ panelRegister,
-    /* blendWrite */ NULL,
+    /* blendWrite */ nullptr,
     /* blendRead */ blendRead,
 };