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

@@ -205,7 +205,7 @@ pxr::HdVolumeFieldDescriptorVector BlenderSceneDelegate::GetVolumeFieldDescripto
 {
   CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 3, "%s", volume_id.GetText());
   VolumeData *v_data = volume_data(volume_id);
-  return v_data->volume_field_descriptors();
+  return v_data->field_descriptors();
 }
 
 void BlenderSceneDelegate::populate(Depsgraph *deps, bContext *cont)

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

@@ -34,8 +34,23 @@ void VolumeData::init()
     return;
   }
   filepath_ = BKE_volume_grids_frame_filepath(volume);
+
+  if (volume->runtime.grids) {
+    const int num_grids = BKE_volume_num_grids(volume);
+    if (num_grids) {
+      for (const int i : IndexRange(num_grids)) {
+        const VolumeGrid *grid = BKE_volume_grid_get_for_read(volume, i);
+        const std::string grid_name = BKE_volume_grid_name(grid);
+
+        field_descriptors_.emplace_back(pxr::TfToken(grid_name),
+                                        pxr::UsdVolImagingTokens->openvdbAsset,
+                                        prim_id.AppendElementString("VF_" + grid_name));
+      }
+    }
+  }
   write_transform();
   write_materials();
+
   BKE_volume_unload(volume);
 }
 
@@ -46,7 +61,7 @@ void VolumeData::insert()
 
   ID_LOG(1, "");
 
-  for (auto &desc : volume_field_descriptors()) {
+  for (auto &desc : field_descriptors_) {
     scene_delegate_->GetRenderIndex().InsertBprim(
         desc.fieldPrimType, scene_delegate_, desc.fieldId);
     ID_LOG(1, "Volume field %s", desc.fieldId.GetText());
@@ -55,10 +70,7 @@ void VolumeData::insert()
 
 void VolumeData::remove()
 {
-  /* NOTE: Is it possible to manipulate a list of fields in Blender?
-   * Also something can happen to file.
-   * Probably we need to store a field list in class. */
-  for (auto &desc : volume_field_descriptors()) {
+  for (auto &desc : field_descriptors_) {
     CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 2, "%s", desc.fieldId.GetText());
     scene_delegate_->GetRenderIndex().RemoveBprim(desc.fieldPrimType, desc.fieldId);
   }
@@ -120,36 +132,9 @@ bool VolumeData::update_visibility()
   return ret;
 }
 
-pxr::HdVolumeFieldDescriptorVector VolumeData::volume_field_descriptors() const
+pxr::HdVolumeFieldDescriptorVector VolumeData::field_descriptors() const
 {
-  Volume *volume = (Volume *)((Object *)id)->data;
-  Main *main = CTX_data_main(scene_delegate_->context);
-
-  if (!volume->runtime.grids) {
-    return pxr::HdVolumeFieldDescriptorVector();
-  }
-
-  if (!BKE_volume_is_loaded(volume) && !BKE_volume_load(volume, main)) {
-    return pxr::HdVolumeFieldDescriptorVector();
-  }
-
-  const int num_grids = BKE_volume_num_grids(volume);
-  if (!num_grids) {
-    return pxr::HdVolumeFieldDescriptorVector();
-  }
-
-  pxr::HdVolumeFieldDescriptorVector volume_field_descriptors;
-  for (const int i : IndexRange(num_grids)) {
-    const VolumeGrid *grid = BKE_volume_grid_get_for_read(volume, i);
-    const std::string grid_name = BKE_volume_grid_name(grid);
-
-    volume_field_descriptors.emplace_back(pxr::TfToken(grid_name),
-                                          pxr::UsdVolImagingTokens->openvdbAsset,
-                                          prim_id.AppendElementString("VF_" + grid_name));
-  }
-
-  BKE_volume_unload(volume);
-  return volume_field_descriptors;
+  return field_descriptors_;
 }
 
 pxr::SdfPath VolumeData::material_id() const

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

@@ -22,7 +22,7 @@ class VolumeData : public ObjectData {
   pxr::VtValue get_data(pxr::SdfPath const &id, pxr::TfToken const &key) const;
   bool update_visibility() override;
 
-  pxr::HdVolumeFieldDescriptorVector volume_field_descriptors() const;
+  pxr::HdVolumeFieldDescriptorVector field_descriptors() const;
   pxr::SdfPath material_id() const;
   void available_materials(Set<pxr::SdfPath> &paths) const;
 
@@ -30,6 +30,7 @@ class VolumeData : public ObjectData {
   void write_materials();
 
   std::string filepath_;
+  pxr::HdVolumeFieldDescriptorVector field_descriptors_;
   MaterialData *mat_data_ = nullptr;
 };