source/blender/render/hydra/scene_delegate/blender_scene_delegate.cc

@@ -23,7 +23,7 @@ pxr::HdMeshTopology BlenderSceneDelegate::GetMeshTopology(pxr::SdfPath const &id
 {
   CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 3, "%s", id.GetText());
   MeshData *m_data = mesh_data(id);
-  return m_data->mesh_topology();
+  return m_data->mesh_topology(id);
 }
 
 pxr::GfMatrix4d BlenderSceneDelegate::GetTransform(pxr::SdfPath const &id)
@@ -46,6 +46,10 @@ pxr::GfMatrix4d BlenderSceneDelegate::GetTransform(pxr::SdfPath const &id)
 pxr::VtValue BlenderSceneDelegate::Get(pxr::SdfPath const &id, pxr::TfToken const &key)
 {
   CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 3, "%s, %s", id.GetText(), key.GetText());
+  MeshData *m_data = mesh_data(id);
+  if (m_data) {
+    return m_data->get_data(id, key);
+  }
   ObjectData *obj_data = object_data(id);
   if (obj_data) {
     return obj_data->get_data(key);
@@ -93,7 +97,7 @@ pxr::HdPrimvarDescriptorVector BlenderSceneDelegate::GetPrimvarDescriptors(
 pxr::SdfPath BlenderSceneDelegate::GetMaterialId(pxr::SdfPath const &rprim_id)
 {
   CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 3, "%s", rprim_id.GetText());
-  return mesh_data(rprim_id)->material_id();
+  return mesh_data(rprim_id)->material_id(rprim_id);
 }
 
 pxr::VtValue BlenderSceneDelegate::GetMaterialResource(pxr::SdfPath const &id)
@@ -122,7 +126,7 @@ bool BlenderSceneDelegate::GetVisible(pxr::SdfPath const &id)
 bool BlenderSceneDelegate::GetDoubleSided(pxr::SdfPath const &id)
 {
   CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 3, "%s", id.GetText());
-  return mesh_data(id)->double_sided();
+  return mesh_data(id)->double_sided(id);
 }
 
 pxr::HdCullStyle BlenderSceneDelegate::GetCullStyle(pxr::SdfPath const &id)
@@ -134,7 +138,7 @@ pxr::HdCullStyle BlenderSceneDelegate::GetCullStyle(pxr::SdfPath const &id)
 pxr::SdfPath BlenderSceneDelegate::GetInstancerId(pxr::SdfPath const &prim_id)
 {
   CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 3, "%s", prim_id.GetText());
-  InstancerData *i_data = instancer_data(prim_id.GetParentPath());
+  InstancerData *i_data = instancer_data(prim_id, true);
   if (i_data) {
     return i_data->prim_id;
   }
@@ -240,11 +244,12 @@ pxr::SdfPath BlenderSceneDelegate::world_prim_id() const
 
 ObjectData *BlenderSceneDelegate::object_data(pxr::SdfPath const &id) const
 {
-  auto it = objects_.find(id);
+  pxr::SdfPath p_id = (id.GetName().find("SM_") == 0) ? id.GetParentPath() : id;
+  auto it = objects_.find(p_id);
   if (it != objects_.end()) {
     return it->second.get();
   }
-  InstancerData *i_data = instancer_data(id, true);
+  InstancerData *i_data = instancer_data(p_id, true);
   if (i_data) {
     return i_data->object_data(id);
   }
@@ -382,7 +387,6 @@ void BlenderSceneDelegate::check_updates()
   data.only_updated = true;
   ITER_BEGIN (DEG_iterator_ids_begin, DEG_iterator_ids_next, DEG_iterator_ids_end, &data, ID *, id)
   {
-
     CLOG_INFO(LOG_RENDER_HYDRA_SCENE,
               2,
               "Update: %s [%s]",
@@ -516,12 +520,8 @@ void BlenderSceneDelegate::remove_unused_objects()
   std::set<pxr::SdfPath> available_materials;
   for (auto &it : objects_) {
     MeshData *m_data = dynamic_cast<MeshData *>(it.second.get());
-    if (!m_data) {
+    if (m_data) {
-      continue;
+      m_data->available_materials(available_materials);
-    }
-    pxr::SdfPath mat_id = m_data->material_id();
-    if (!mat_id.IsEmpty()) {
-      available_materials.insert(mat_id);
     }
   }
   for (auto &it : instancers_) {

source/blender/render/hydra/scene_delegate/instancer.cc

@@ -36,7 +36,7 @@ bool InstancerData::is_supported(Object *object)
 void InstancerData::init()
 {
   ID_LOG(2, "");
-  set_instances();
+  write_instances();
 }
 
 void InstancerData::insert()
@@ -68,7 +68,7 @@ void InstancerData::update()
       (object->data && ((ID *)object->data)->recalc & ID_RECALC_GEOMETRY) ||
       id->recalc & ID_RECALC_TRANSFORM)
   {
-    set_instances();
+    write_instances();
     scene_delegate_->GetRenderIndex().GetChangeTracker().MarkInstancerDirty(
         prim_id, pxr::HdChangeTracker::AllDirty);
   }
@@ -92,8 +92,9 @@ bool InstancerData::update_visibility()
     change_tracker.MarkInstancerDirty(prim_id, pxr::HdChangeTracker::DirtyVisibility);
     for (auto &it : mesh_instances_) {
       it.second.data->visible = visible;
-      change_tracker.MarkRprimDirty(it.second.data->prim_id,
+      for (auto &p : it.second.data->submesh_paths()) {
-                                    pxr::HdChangeTracker::DirtyVisibility);
+        change_tracker.MarkRprimDirty(p, pxr::HdChangeTracker::DirtyVisibility);
+      }
     }
     char name[16];
     for (auto &it : light_instances_) {
@@ -109,9 +110,9 @@ bool InstancerData::update_visibility()
 
 pxr::GfMatrix4d InstancerData::get_transform(pxr::SdfPath const &id) const
 {
-  if (id.GetPathElementCount() == 4) {
+  LightInstance *l_inst = light_instance(id);
-    const auto &inst = light_instances_.find(id.GetParentPath())->second;
+  if (l_inst) {
-    return inst.transforms[light_prim_id_index(id)];
+    return l_inst->transforms[light_prim_id_index(id)];
   }
 
   /* Mesh instance transform must be identity */
@@ -131,18 +132,18 @@ pxr::HdPrimvarDescriptorVector InstancerData::primvar_descriptors(
 
 pxr::VtIntArray InstancerData::indices(pxr::SdfPath const &id) const
 {
-  return mesh_instances_.find(id)->second.indices;
+  return mesh_instance(id)->indices;
 }
 
 ObjectData *InstancerData::object_data(pxr::SdfPath const &id) const
 {
-  auto m_it = mesh_instances_.find(id);
+  MeshInstance *m_inst = mesh_instance(id);
-  if (m_it != mesh_instances_.end()) {
+  if (m_inst) {
-    return m_it->second.data.get();
+    return m_inst->data.get();
   }
-  auto l_it = light_instances_.find(id.GetParentPath());
+  LightInstance *l_inst = light_instance(id);
-  if (l_it != light_instances_.end()) {
+  if (l_inst) {
-    return l_it->second.data.get();
+    return l_inst->data.get();
   }
   return nullptr;
 }
@@ -151,7 +152,9 @@ pxr::SdfPathVector InstancerData::prototypes() const
 {
   pxr::SdfPathVector paths;
   for (auto &it : mesh_instances_) {
-    paths.push_back(it.first);
+    for (auto &p : it.second.data->submesh_paths()) {
+      paths.push_back(p);
+    }
   }
   return paths;
 }
@@ -159,25 +162,25 @@ pxr::SdfPathVector InstancerData::prototypes() const
 void InstancerData::check_update(Object *object)
 {
   pxr::SdfPath path = object_prim_id(object);
-  auto m_it = mesh_instances_.find(path);
+  MeshInstance *m_inst = mesh_instance(path);
-  if (m_it != mesh_instances_.end()) {
+  if (m_inst) {
-    m_it->second.data->update();
+    m_inst->data->update();
 
-    if (m_it->second.data->id->recalc & ID_RECALC_TRANSFORM) {
+    if (m_inst->data->id->recalc & ID_RECALC_TRANSFORM) {
-      set_instances();
+      write_instances();
       scene_delegate_->GetRenderIndex().GetChangeTracker().MarkInstancerDirty(
           prim_id, pxr::HdChangeTracker::AllDirty);
     }
     return;
   }
 
-  auto l_it = light_instances_.find(path);
+  LightInstance *l_inst = light_instance(path);
-  if (l_it != light_instances_.end()) {
+  if (l_inst) {
-    Object *obj = (Object *)l_it->second.data->id;
+    Object *obj = (Object *)l_inst->data->id;
     if (obj->id.recalc & (ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY) ||
         ((ID *)obj->data)->recalc & ID_RECALC_GEOMETRY)
     {
-      set_instances();
+      write_instances();
     }
     return;
   }
@@ -196,7 +199,7 @@ void InstancerData::check_remove(std::set<std::string> &available_objects)
     ret = true;
   }
   if (ret) {
-    set_instances();
+    write_instances();
     scene_delegate_->GetRenderIndex().GetChangeTracker().MarkInstancerDirty(
         prim_id, pxr::HdChangeTracker::AllDirty);
   }
@@ -216,16 +219,13 @@ void InstancerData::check_remove(std::set<std::string> &available_objects)
 void InstancerData::available_materials(std::set<pxr::SdfPath> &paths) const
 {
   for (auto &it : mesh_instances_) {
-    pxr::SdfPath mat_id = ((MeshData *)it.second.data.get())->material_id();
+    ((MeshData *)it.second.data.get())->available_materials(paths);
-    if (!mat_id.IsEmpty()) {
-      paths.insert(mat_id);
-    }
   }
 }
 
 void InstancerData::update_as_parent()
 {
-  set_instances();
+  write_instances();
   scene_delegate_->GetRenderIndex().GetChangeTracker().MarkInstancerDirty(
       prim_id, pxr::HdChangeTracker::AllDirty);
 }
@@ -259,7 +259,7 @@ int InstancerData::light_prim_id_index(pxr::SdfPath const &id) const
   return index;
 }
 
-void InstancerData::set_instances()
+void InstancerData::write_instances()
 {
   mesh_transforms_.clear();
   for (auto &it : mesh_instances_) {
@@ -279,31 +279,23 @@ void InstancerData::set_instances()
 
     pxr::SdfPath p_id = object_prim_id(ob);
     if (ob->type == OB_LAMP) {
-      LightInstance *inst;
+      LightInstance *inst = light_instance(p_id);
-      auto it = light_instances_.find(p_id);
+      if (!inst) {
-      if (it == light_instances_.end()) {
         inst = &light_instances_[p_id];
         inst->data = std::make_unique<LightData>(scene_delegate_, ob, p_id);
         inst->data->init();
       }
-      else {
-        inst = &it->second;
-      }
       ID_LOG(2, "Light %s %d", inst->data->id->name, inst->transforms.size());
       inst->transforms.push_back(gf_matrix_from_transform(dupli->mat));
     }
     else {
-      MeshInstance *inst;
+      MeshInstance *inst = mesh_instance(p_id);
-      auto it = mesh_instances_.find(p_id);
+      if (!inst) {
-      if (it == mesh_instances_.end()) {
         inst = &mesh_instances_[p_id];
         inst->data = std::make_unique<MeshData>(scene_delegate_, ob, p_id);
         inst->data->init();
         inst->data->insert();
       }
-      else {
-        inst = &it->second;
-      }
       ID_LOG(2, "Mesh %s %d", inst->data->id->name, mesh_transforms_.size());
       inst->indices.push_back(mesh_transforms_.size());
       mesh_transforms_.push_back(gf_matrix_from_transform(dupli->mat));
@@ -386,4 +378,22 @@ void InstancerData::update_light_instance(LightInstance &inst)
   }
 }
 
+InstancerData::MeshInstance *InstancerData::mesh_instance(pxr::SdfPath const &id) const
+{
+  auto it = mesh_instances_.find(id.GetPathElementCount() == 4 ? id.GetParentPath() : id);
+  if (it == mesh_instances_.end()) {
+    return nullptr;
+  }
+  return const_cast<MeshInstance *>(&it->second);
+}
+
+InstancerData::LightInstance *InstancerData::light_instance(pxr::SdfPath const &id) const
+{
+  auto it = light_instances_.find(id.GetPathElementCount() == 4 ? id.GetParentPath() : id);
+  if (it == light_instances_.end()) {
+    return nullptr;
+  }
+  return const_cast<LightInstance *>(&it->second);
+}
+
 }  // namespace blender::render::hydra

source/blender/render/hydra/scene_delegate/instancer.h

@@ -49,8 +49,10 @@ class InstancerData : public ObjectData {
   pxr::SdfPath object_prim_id(Object *object) const;
   pxr::SdfPath light_prim_id(LightInstance const &inst, int index) const;
   int light_prim_id_index(pxr::SdfPath const &id) const;
-  void set_instances();
+  void write_instances();
   void update_light_instance(LightInstance &inst);
+  MeshInstance *mesh_instance(pxr::SdfPath const &id) const;
+  LightInstance *light_instance(pxr::SdfPath const &id) const;
 
   pxr::TfHashMap<pxr::SdfPath, MeshInstance, pxr::SdfPath::Hash> mesh_instances_;
   pxr::TfHashMap<pxr::SdfPath, LightInstance, pxr::SdfPath::Hash> light_instances_;

source/blender/render/hydra/scene_delegate/mesh.cc

@@ -29,89 +29,72 @@ void MeshData::init()
   if (object->type == OB_MESH && object->mode == OB_MODE_OBJECT &&
       BLI_listbase_is_empty(&object->modifiers))
   {
-    write_mesh((Mesh *)object->data);
+    write_submeshes((Mesh *)object->data);
   }
   else {
     Mesh *mesh = BKE_object_to_mesh(nullptr, object, false);
     if (mesh) {
-      write_mesh(mesh);
+      write_submeshes(mesh);
     }
     BKE_object_to_mesh_clear(object);
   }
 
-  write_material();
   write_transform();
+  write_materials();
 }
 
 void MeshData::insert()
 {
-  if (face_vertex_counts_.empty()) {
+  /* Empty, because insertion of rprims happen in write_submeshes() */
-    return;
-  }
-
-  ID_LOG(2, "");
-  scene_delegate_->GetRenderIndex().InsertRprim(
-      pxr::HdPrimTypeTokens->mesh, scene_delegate_, prim_id);
 }
 
 void MeshData::remove()
 {
-  if (!scene_delegate_->GetRenderIndex().HasRprim(prim_id)) {
+  for (int i = 0; i < submeshes_.size(); ++i) {
-    return;
+    scene_delegate_->GetRenderIndex().RemoveRprim(submesh_prim_id(i));
+    CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 2, "%s: %d", prim_id.GetText(), i);
   }
-
-  CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 2, "%s", prim_id.GetText());
-  scene_delegate_->GetRenderIndex().RemoveRprim(prim_id);
 }
 
 void MeshData::update()
 {
   Object *object = (Object *)id;
-  pxr::HdDirtyBits bits = pxr::HdChangeTracker::Clean;
   if ((id->recalc & ID_RECALC_GEOMETRY) || (((ID *)object->data)->recalc & ID_RECALC_GEOMETRY)) {
     init();
-    bits = pxr::HdChangeTracker::AllDirty;
+    return;
   }
-  else {
+
-    if (id->recalc & ID_RECALC_SHADING) {
+  pxr::HdDirtyBits bits = pxr::HdChangeTracker::Clean;
-      write_material();
+  if (id->recalc & ID_RECALC_SHADING) {
-      bits |= pxr::HdChangeTracker::DirtyMaterialId | pxr::HdChangeTracker::DirtyDoubleSided;
+    write_materials();
-    }
+    bits |= pxr::HdChangeTracker::DirtyMaterialId | pxr::HdChangeTracker::DirtyDoubleSided;
-    if (id->recalc & ID_RECALC_TRANSFORM) {
+  }
-      write_transform();
+  if (id->recalc & ID_RECALC_TRANSFORM) {
-      bits |= pxr::HdChangeTracker::DirtyTransform;
+    write_transform();
-    }
+    bits |= pxr::HdChangeTracker::DirtyTransform;
   }
 
   if (bits == pxr::HdChangeTracker::Clean) {
     return;
   }
 
-  if (!scene_delegate_->GetRenderIndex().HasRprim(prim_id)) {
+  for (int i = 0; i < submeshes_.size(); ++i) {
-    insert();
+    scene_delegate_->GetRenderIndex().GetChangeTracker().MarkRprimDirty(submesh_prim_id(i), bits);
-    return;
+    ID_LOG(2, "%d", i);
   }
-
-  if (face_vertex_counts_.empty()) {
-    /* Remove prim without faces */
-    remove();
-    return;
-  }
-  ID_LOG(2, "");
-  scene_delegate_->GetRenderIndex().GetChangeTracker().MarkRprimDirty(prim_id, bits);
 }
 
-pxr::VtValue MeshData::get_data(pxr::TfToken const &key) const
+pxr::VtValue MeshData::get_data(pxr::SdfPath const &id, pxr::TfToken const &key) const
 {
   pxr::VtValue ret;
   if (key == pxr::HdTokens->points) {
     ret = vertices_;
   }
   else if (key == pxr::HdTokens->normals) {
-    ret = normals_;
+    ret = submesh(id).normals;
   }
   else if (key == pxr::HdPrimvarRoleTokens->textureCoordinate) {
-    ret = uvs_;
+    ret = submesh(id).uvs;
   }
   return ret;
 }
@@ -120,19 +103,22 @@ bool MeshData::update_visibility()
 {
   bool ret = ObjectData::update_visibility();
   if (ret) {
-    ID_LOG(2, "");
+    for (int i = 0; i < submeshes_.size(); ++i) {
-    scene_delegate_->GetRenderIndex().GetChangeTracker().MarkRprimDirty(
+      scene_delegate_->GetRenderIndex().GetChangeTracker().MarkRprimDirty(
-        prim_id, pxr::HdChangeTracker::DirtyVisibility);
+          submesh_prim_id(i), pxr::HdChangeTracker::DirtyVisibility);
+      ID_LOG(2, "%d", i);
+    }
   }
   return ret;
 }
 
-pxr::HdMeshTopology MeshData::mesh_topology() const
+pxr::HdMeshTopology MeshData::mesh_topology(pxr::SdfPath const &id) const
 {
+  const SubMesh &sm = submesh(id);
   return pxr::HdMeshTopology(pxr::PxOsdOpenSubdivTokens->none,
                              pxr::HdTokens->rightHanded,
-                             face_vertex_counts_,
+                             sm.face_vertex_counts,
-                             face_vertex_indices_);
+                             sm.face_vertex_indices);
 }
 
 pxr::HdPrimvarDescriptorVector MeshData::primvar_descriptors(
@@ -145,11 +131,11 @@ pxr::HdPrimvarDescriptorVector MeshData::primvar_descriptors(
     }
   }
   else if (interpolation == pxr::HdInterpolationFaceVarying) {
-    if (!normals_.empty()) {
+    if (!submeshes_[0].normals.empty()) {
       primvars.emplace_back(
           pxr::HdTokens->normals, interpolation, pxr::HdPrimvarRoleTokens->normal);
     }
-    if (!uvs_.empty()) {
+    if (!submeshes_[0].uvs.empty()) {
       primvars.emplace_back(pxr::HdPrimvarRoleTokens->textureCoordinate,
                             interpolation,
                             pxr::HdPrimvarRoleTokens->textureCoordinate);
@@ -158,116 +144,171 @@ pxr::HdPrimvarDescriptorVector MeshData::primvar_descriptors(
   return primvars;
 }
 
-pxr::SdfPath MeshData::material_id() const
+pxr::SdfPath MeshData::material_id(pxr::SdfPath const &id) const
 {
-  if (!mat_data_) {
+  const SubMesh &sm = submesh(id);
+  if (!sm.mat_data) {
     return pxr::SdfPath();
   }
-  return mat_data_->prim_id;
+  return sm.mat_data->prim_id;
 }
 
-bool MeshData::double_sided() const
+bool MeshData::double_sided(pxr::SdfPath const &id) const
 {
-  if (mat_data_) {
+  const SubMesh &sm = submesh(id);
-    return mat_data_->double_sided;
+  if (sm.mat_data) {
+    return sm.mat_data->double_sided;
   }
   return true;
 }
 
 void MeshData::update_double_sided(MaterialData *mat_data)
 {
-  if (mat_data_ == mat_data) {
+  for (int i = 0; i < submeshes_.size(); ++i) {
-    ID_LOG(2, "");
+    if (submeshes_[i].mat_data == mat_data) {
-    scene_delegate_->GetRenderIndex().GetChangeTracker().MarkRprimDirty(
+      scene_delegate_->GetRenderIndex().GetChangeTracker().MarkRprimDirty(
-        prim_id, pxr::HdChangeTracker::DirtyDoubleSided);
+          submesh_prim_id(i), pxr::HdChangeTracker::DirtyDoubleSided);
-  }
+      ID_LOG(2, "%d", i);
-}
-
-void MeshData::write_mesh(Mesh *mesh)
-{
-  face_vertex_counts_.clear();
-  face_vertex_indices_.clear();
-  vertices_.clear();
-  normals_.clear();
-  uvs_.clear();
-
-  BKE_mesh_calc_normals_split(mesh);
-  int tris_len = BKE_mesh_runtime_looptri_len(mesh);
-  if (tris_len == 0) {
-    return;
-  }
-
-  blender::Span<MLoopTri> loopTris = mesh->looptris();
-
-  /* face_vertex_counts */
-  face_vertex_counts_ = pxr::VtIntArray(tris_len, 3);
-
-  /* face_vertex_indices */
-  blender::Span<int> corner_verts = mesh->corner_verts();
-  face_vertex_indices_.reserve(loopTris.size() * 3);
-  for (MLoopTri lt : loopTris) {
-    face_vertex_indices_.push_back(corner_verts[lt.tri[0]]);
-    face_vertex_indices_.push_back(corner_verts[lt.tri[1]]);
-    face_vertex_indices_.push_back(corner_verts[lt.tri[2]]);
-  }
-
-  /* vertices */
-  vertices_.reserve(mesh->totvert);
-  blender::Span<blender::float3> verts = mesh->vert_positions();
-  for (blender::float3 v : verts) {
-    vertices_.push_back(pxr::GfVec3f(v.x, v.y, v.z));
-  }
-
-  write_normals(mesh);
-  write_uv_maps(mesh);
-}
-
-void MeshData::write_material()
-{
-  Object *object = (Object *)id;
-  Material *mat = nullptr;
-  if (BKE_object_material_count_eval(object) > 0) {
-    mat = BKE_object_material_get_eval(object, object->actcol);
-  }
-
-  if (!mat) {
-    mat_data_ = nullptr;
-    return;
-  }
-  pxr::SdfPath p_id = scene_delegate_->material_prim_id(mat);
-  mat_data_ = scene_delegate_->material_data(p_id);
-  if (!mat_data_) {
-    scene_delegate_->materials_[p_id] = std::make_unique<MaterialData>(scene_delegate_, mat, p_id);
-    mat_data_ = scene_delegate_->material_data(p_id);
-    mat_data_->init();
-    mat_data_->insert();
-  }
-}
-
-void MeshData::write_uv_maps(Mesh *mesh)
-{
-  blender::Span<MLoopTri> loopTris = mesh->looptris();
-  const float(*luvs)[2] = (float(*)[2])CustomData_get_layer(&mesh->ldata, CD_PROP_FLOAT2);
-  if (luvs) {
-    uvs_.reserve(loopTris.size() * 3);
-    for (MLoopTri lt : loopTris) {
-      uvs_.push_back(pxr::GfVec2f(luvs[lt.tri[0]]));
-      uvs_.push_back(pxr::GfVec2f(luvs[lt.tri[1]]));
-      uvs_.push_back(pxr::GfVec2f(luvs[lt.tri[2]]));
     }
   }
 }
 
-void MeshData::write_normals(Mesh *mesh)
+void MeshData::available_materials(std::set<pxr::SdfPath> &paths) const
 {
-  blender::Span<MLoopTri> loopTris = mesh->looptris();
+  for (auto &sm : submeshes_) {
+    if (sm.mat_data && !sm.mat_data->prim_id.IsEmpty()) {
+      paths.insert(sm.mat_data->prim_id);
+    }
+  }
+}
+
+pxr::SdfPathVector MeshData::submesh_paths() const
+{
+  pxr::SdfPathVector ret;
+  for (int i = 0; i < submeshes_.size(); ++i) {
+    ret.push_back(submesh_prim_id(i));
+  }
+  return ret;
+}
+
+pxr::SdfPath MeshData::submesh_prim_id(int index) const
+{
+  char name[16];
+  snprintf(name, 16, "SM_%04x", index);
+  return prim_id.AppendElementString(name);
+}
+
+const MeshData::SubMesh &MeshData::submesh(pxr::SdfPath const &id) const
+{
+  int index;
+  sscanf(id.GetName().c_str(), "SM_%x", &index);
+  return submeshes_[index];
+}
+
+void MeshData::write_submeshes(Mesh *mesh)
+{
+  int sub_meshes_prev_count = submeshes_.size();
+  submeshes_.clear();
+  vertices_.clear();
+
+  /* Insert base submeshes */
+  int mat_count = BKE_object_material_count_eval((Object *)id);
+  for (int i = 0; i < std::max(mat_count, 1); ++i) {
+    SubMesh sm;
+    sm.mat_index = i;
+    submeshes_.push_back(sm);
+  }
+
+  /* Fill submeshes data */
+  const int *material_indices = BKE_mesh_material_indices(mesh);
+  const int *looptri_polys = BKE_mesh_runtime_looptri_polys_ensure(mesh);
+  blender::Span<int> corner_verts = mesh->corner_verts();
+  blender::Span<MLoopTri> looptris = mesh->looptris();
+
+  BKE_mesh_calc_normals_split(mesh);
   const float(*lnors)[3] = (float(*)[3])CustomData_get_layer(&mesh->ldata, CD_NORMAL);
-  if (lnors) {
+  const float(*luvs)[2] = (float(*)[2])CustomData_get_layer(&mesh->ldata, CD_PROP_FLOAT2);
-    normals_.reserve(loopTris.size() * 3);
+
-    for (MLoopTri lt : loopTris) {
+  for (size_t i = 0; i < looptris.size(); ++i) {
-      normals_.push_back(pxr::GfVec3f(lnors[lt.tri[0]]));
+    int mat_ind = material_indices ? material_indices[looptri_polys[i]] : 0;
-      normals_.push_back(pxr::GfVec3f(lnors[lt.tri[1]]));
+    const MLoopTri &lt = looptris[i];
-      normals_.push_back(pxr::GfVec3f(lnors[lt.tri[2]]));
+    SubMesh &sm = submeshes_[mat_ind];
+
+    sm.face_vertex_counts.push_back(3);
+    sm.face_vertex_indices.push_back(corner_verts[lt.tri[0]]);
+    sm.face_vertex_indices.push_back(corner_verts[lt.tri[1]]);
+    sm.face_vertex_indices.push_back(corner_verts[lt.tri[2]]);
+
+    if (lnors) {
+      sm.normals.push_back(pxr::GfVec3f(lnors[lt.tri[0]]));
+      sm.normals.push_back(pxr::GfVec3f(lnors[lt.tri[1]]));
+      sm.normals.push_back(pxr::GfVec3f(lnors[lt.tri[2]]));
+    }
+
+    if (luvs) {
+      sm.uvs.push_back(pxr::GfVec2f(luvs[lt.tri[0]]));
+      sm.uvs.push_back(pxr::GfVec2f(luvs[lt.tri[1]]));
+      sm.uvs.push_back(pxr::GfVec2f(luvs[lt.tri[2]]));
+    }
+  }
+
+  /* Remove submeshes without faces */
+  for (auto it = submeshes_.begin(); it != submeshes_.end();) {
+    if (it->face_vertex_counts.empty()) {
+      it = submeshes_.erase(it);
+    }
+    else {
+      ++it;
+    }
+  }
+
+  if (!submeshes_.empty()) {
+    /* vertices */
+    vertices_.reserve(mesh->totvert);
+    blender::Span<blender::float3> verts = mesh->vert_positions();
+    for (blender::float3 v : verts) {
+      vertices_.push_back(pxr::GfVec3f(v.x, v.y, v.z));
+    }
+  }
+
+  /* Update prims in render index */
+  auto &render_index = scene_delegate_->GetRenderIndex();
+  int i;
+  for (i = 0; i < submeshes_.size(); ++i) {
+    pxr::SdfPath p = submesh_prim_id(i);
+    if (i < sub_meshes_prev_count) {
+      render_index.GetChangeTracker().MarkRprimDirty(p, pxr::HdChangeTracker::AllDirty);
+      ID_LOG(2, "Update %d", i);
+    }
+    else {
+      render_index.InsertRprim(pxr::HdPrimTypeTokens->mesh, scene_delegate_, p);
+      ID_LOG(2, "Insert %d", i);
+    }
+  }
+  for (; i < sub_meshes_prev_count; ++i) {
+    render_index.RemoveRprim(submesh_prim_id(i));
+    ID_LOG(2, "Remove %d", i);
+  }
+}
+
+void MeshData::write_materials()
+{
+  Object *object = (Object *)id;
+  for (int i = 0; i < submeshes_.size(); ++i) {
+    SubMesh &m = submeshes_[i];
+    Material *mat = BKE_object_material_get_eval(object, m.mat_index + 1);
+    if (!mat) {
+      m.mat_data = nullptr;
+      continue;
+    }
+    pxr::SdfPath p_id = scene_delegate_->material_prim_id(mat);
+    m.mat_data = scene_delegate_->material_data(p_id);
+    if (!m.mat_data) {
+      scene_delegate_->materials_[p_id] = std::make_unique<MaterialData>(
+          scene_delegate_, mat, p_id);
+      m.mat_data = scene_delegate_->material_data(p_id);
+      m.mat_data->init();
+      m.mat_data->insert();
     }
   }
 }

source/blender/render/hydra/scene_delegate/mesh.h

@@ -14,6 +14,15 @@
 namespace blender::render::hydra {
 
 class MeshData : public ObjectData {
+  struct SubMesh {
+    pxr::VtIntArray face_vertex_counts;
+    pxr::VtIntArray face_vertex_indices;
+    pxr::VtVec3fArray normals;
+    pxr::VtVec2fArray uvs;
+    int mat_index = 0;
+    MaterialData *mat_data = nullptr;
+  };
+
  public:
   MeshData(BlenderSceneDelegate *scene_delegate, Object *object, pxr::SdfPath const &prim_id);
 
@@ -22,30 +31,27 @@ class MeshData : public ObjectData {
   void remove() override;
   void update() override;
 
-  pxr::VtValue get_data(pxr::TfToken const &key) const override;
+  pxr::VtValue get_data(pxr::SdfPath const &id, pxr::TfToken const &key) const;
   bool update_visibility() override;
 
-  pxr::HdMeshTopology mesh_topology() const;
+  pxr::HdMeshTopology mesh_topology(pxr::SdfPath const &id) const;
   pxr::HdPrimvarDescriptorVector primvar_descriptors(pxr::HdInterpolation interpolation) const;
-  pxr::SdfPath material_id() const;
+  pxr::SdfPath material_id(pxr::SdfPath const &id) const;
-  bool double_sided() const;
+  bool double_sided(pxr::SdfPath const &id) const;
   void update_double_sided(MaterialData *mat_data);
+  void available_materials(std::set<pxr::SdfPath> &paths) const;
+  pxr::SdfPathVector submesh_paths() const;
 
   pxr::HdCullStyle cull_style = pxr::HdCullStyleBackUnlessDoubleSided;
 
  private:
-  void write_mesh(Mesh *mesh);
+  pxr::SdfPath submesh_prim_id(int index) const;
-  void write_material();
+  const SubMesh &submesh(pxr::SdfPath const &id) const;
-  void write_uv_maps(Mesh *mesh);
+  void write_submeshes(Mesh *mesh);
-  void write_normals(Mesh *mesh);
+  void write_materials();
 
-  pxr::VtIntArray face_vertex_counts_;
-  pxr::VtIntArray face_vertex_indices_;
   pxr::VtVec3fArray vertices_;
-  pxr::VtVec2fArray uvs_;
+  std::vector<SubMesh> submeshes_;
-  pxr::VtVec3fArray normals_;
-
-  MaterialData *mat_data_ = nullptr;
 };
 
 }  // namespace blender::render::hydra