source/blender/blenkernel/BKE_blender_version.h

@@ -29,7 +29,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 33
+#define BLENDER_FILE_SUBVERSION 34
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and cancel loading the file, showing a warning to

source/blender/blenkernel/BKE_mesh_legacy_convert.hh

@@ -72,7 +72,7 @@ void BKE_mesh_legacy_convert_polys_to_offsets(Mesh *mesh);
 
 void BKE_mesh_legacy_convert_loops_to_corners(Mesh *mesh);
 
-void BKE_mesh_legacy_face_map_to_generic(Mesh *mesh);
+void BKE_mesh_legacy_face_map_to_generic(Main *bmain);
 
 /**
  * Recreate #MFace Tessellation.

source/blender/blenkernel/intern/mesh_legacy_convert.cc

@@ -16,11 +16,14 @@
 #include "DNA_meshdata_types.h"
 #include "DNA_object_types.h"
 
+#include "BLI_array_utils.hh"
+#include "BLI_listbase.h"
 #include "BLI_map.hh"
 #include "BLI_math_geom.h"
 #include "BLI_math_matrix.h"
 #include "BLI_math_vector_types.hh"
 #include "BLI_memarena.h"
+#include "BLI_multi_value_map.hh"
 #include "BLI_polyfill_2d.h"
 #include "BLI_resource_scope.hh"
 #include "BLI_string.h"
@@ -30,6 +33,7 @@
 #include "BKE_attribute.hh"
 #include "BKE_customdata.h"
 #include "BKE_global.h"
+#include "BKE_main.h"
 #include "BKE_mesh.hh"
 #include "BKE_mesh_legacy_convert.hh"
 #include "BKE_multires.hh"
@@ -1345,18 +1349,18 @@ void BKE_mesh_legacy_face_set_to_generic(Mesh *mesh)
 /** \name Face Map Conversion
  * \{ */
 
-void BKE_mesh_legacy_face_map_to_generic(Mesh *mesh)
+static void move_face_map_data_to_attributes(Mesh *mesh)
 {
   using namespace blender;
   if (mesh->attributes().contains("face_maps")) {
     return;
   }
-  void *data = nullptr;
+  int *data = nullptr;
   const ImplicitSharingInfo *sharing_info = nullptr;
   for (const int i : IndexRange(mesh->face_data.totlayer)) {
     CustomDataLayer &layer = mesh->face_data.layers[i];
     if (layer.type == CD_FACEMAP) {
-      data = layer.data;
+      data = static_cast<int *>(layer.data);
       sharing_info = layer.sharing_info;
       layer.data = nullptr;
       layer.sharing_info = nullptr;
@@ -1364,13 +1368,53 @@ void BKE_mesh_legacy_face_map_to_generic(Mesh *mesh)
       break;
     }
   }
-  if (data != nullptr) {
-    CustomData_add_layer_named_with_data(
-        &mesh->face_data, CD_PROP_INT32, data, mesh->faces_num, "face_maps", sharing_info);
+  if (!data) {
+    return;
   }
+
+  CustomData_add_layer_named_with_data(
+      &mesh->face_data, CD_PROP_INT32, data, mesh->faces_num, "face_maps", sharing_info);
   if (sharing_info != nullptr) {
     sharing_info->remove_user_and_delete_if_last();
   }
+
+  MultiValueMap<int, int> groups;
+  for (const int i : IndexRange(mesh->faces_num)) {
+    if (data[i] == -1) {
+      /* -1 values "didn't have" a face map. */
+      continue;
+    }
+    groups.add(data[i], i);
+  }
+
+  bke::MutableAttributeAccessor attributes = mesh->attributes_for_write();
+  for (const auto item : groups.items()) {
+    bke::SpanAttributeWriter<bool> attribute = attributes.lookup_or_add_for_write_span<bool>(
+        ".temp_face_map_" + std::to_string(item.key), ATTR_DOMAIN_FACE);
+    if (attribute) {
+      attribute.span.fill_indices(item.value.as_span(), true);
+      attribute.finish();
+    }
+  }
+}
+
+void BKE_mesh_legacy_face_map_to_generic(Main *bmain)
+{
+  LISTBASE_FOREACH (Mesh *, mesh, &bmain->meshes) {
+    move_face_map_data_to_attributes(mesh);
+  }
+
+  LISTBASE_FOREACH (Object *, object, &bmain->objects) {
+    if (object->type != OB_MESH) {
+      continue;
+    }
+    Mesh *mesh = static_cast<Mesh *>(object->data);
+    int i;
+    LISTBASE_FOREACH_INDEX (bFaceMap *, face_map, &object->fmaps, i) {
+      mesh->attributes_for_write().rename(".temp_face_map_" + std::to_string(i), face_map->name);
+    }
+    BLI_freelistN(&object->fmaps);
+  }
 }
 
 /** \} */

source/blender/blenkernel/intern/object.cc

@@ -707,6 +707,7 @@ static void object_blend_read_data(BlendDataReader *reader, ID *id)
 
   /* Only for versioning, vertex group names are now stored on object data. */
   BLO_read_list(reader, &ob->defbase);
+  BLO_read_list(reader, &ob->fmaps);
 
   /* XXX deprecated - old animation system <<< */
   direct_link_nlastrips(reader, &ob->nlastrips);

source/blender/blenloader/intern/versioning_400.cc

@@ -311,6 +311,10 @@ void do_versions_after_linking_400(FileData *fd, Main *bmain)
     }
   }
 
+  if (!MAIN_VERSION_FILE_ATLEAST(bmain, 400, 34)) {
+    BKE_mesh_legacy_face_map_to_generic(bmain);
+  }
+
   /**
    * Versioning code until next subversion bump goes here.
    *
@@ -1097,9 +1101,6 @@ void blo_do_versions_400(FileData *fd, Library * /*lib*/, Main *bmain)
   }
 
   if (!MAIN_VERSION_FILE_ATLEAST(bmain, 400, 6)) {
-    LISTBASE_FOREACH (Mesh *, mesh, &bmain->meshes) {
-      BKE_mesh_legacy_face_map_to_generic(mesh);
-    }
     FOREACH_NODETREE_BEGIN (bmain, ntree, id) {
       versioning_replace_legacy_glossy_node(ntree);
       versioning_remove_microfacet_sharp_distribution(ntree);

source/blender/makesdna/DNA_object_types.h

@@ -60,6 +60,16 @@ typedef struct bDeformGroup {
   char flag, _pad0[7];
 } bDeformGroup;
 
+#ifdef DNA_DEPRECATED_ALLOW
+typedef struct bFaceMap {
+  struct bFaceMap *next, *prev;
+  /** MAX_VGROUP_NAME. */
+  char name[64];
+  char flag;
+  char _pad0[7];
+} bFaceMap;
+#endif
+
 #define MAX_VGROUP_NAME 64
 
 /** #bDeformGroup::flag */
@@ -346,6 +356,7 @@ typedef struct Object {
   ListBase constraintChannels DNA_DEPRECATED; /* XXX deprecated... old animation system */
   ListBase effect DNA_DEPRECATED;             /* XXX deprecated... keep for readfile */
   ListBase defbase DNA_DEPRECATED;            /* Only for versioning, moved to object data. */
+  ListBase fmaps DNA_DEPRECATED;              /* For versioning, moved to generic attributes. */
   /** List of ModifierData structures. */
   ListBase modifiers;
   /** List of GpencilModifierData structures. */