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

@@ -63,6 +63,10 @@ pxr::VtValue BlenderSceneDelegate::Get(pxr::SdfPath const &id, pxr::TfToken cons
   if (c_data) {
     return c_data->get_data(id, key);
   }
+  VolumeData *vol_data = volume_data(id);
+  if (vol_data) {
+    return vol_data->get_data(id, key);
+  }
   ObjectData *obj_data = object_data(id);
   if (obj_data) {
     return obj_data->get_data(key);
@@ -193,10 +197,10 @@ pxr::GfMatrix4d BlenderSceneDelegate::GetInstancerTransform(pxr::SdfPath const &
 }
 
 pxr::HdVolumeFieldDescriptorVector BlenderSceneDelegate::GetVolumeFieldDescriptors(
-    pxr::SdfPath const &volume_Id)
+    pxr::SdfPath const &volume_id)
 {
-  CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 3, "%s", volume_Id.GetText());
-  VolumeData *v_data = volume_data(volume_Id);
+  CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 3, "%s", volume_id.GetText());
+  VolumeData *v_data = volume_data(volume_id);
   return v_data->volume_field_descriptors();
 }
 
@@ -280,7 +284,7 @@ pxr::SdfPath BlenderSceneDelegate::world_prim_id() const
 
 ObjectData *BlenderSceneDelegate::object_data(pxr::SdfPath const &id) const
 {
-  pxr::SdfPath p_id = (id.GetName().find("SM_") == 0) ? id.GetParentPath() : id;
+  pxr::SdfPath p_id = (id.GetName().find("SM_") == 0 || id.GetName().find("field_") == 0) ? id.GetParentPath() : id;
   auto obj_data = objects_.lookup_ptr(p_id);
   if (obj_data) {
     return obj_data->get();

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

@@ -62,7 +62,7 @@ class BlenderSceneDelegate : public pxr::HdSceneDelegate {
                                      pxr::SdfPath const &prototype_id) override;
   pxr::GfMatrix4d GetInstancerTransform(pxr::SdfPath const &instancer_id) override;
   pxr::HdVolumeFieldDescriptorVector GetVolumeFieldDescriptors(
-      pxr::SdfPath const &volume_Id) override;
+      pxr::SdfPath const &volume_id) override;
 
   void populate(Depsgraph *depsgraph, bContext *context);
   void clear();

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

@@ -3,9 +3,15 @@
 
 #include <pxr/imaging/hd/tokens.h>
 #include <pxr/imaging/hd/volume.h>
+#include <pxr/imaging/hd/bprim.h>
+#include <pxr/imaging/hd/volumeFieldSchema.h>
+#include <pxr/usd/usdHydra/tokens.h>
+#include <pxr/usd/usdVol/tokens.h>
+#include <pxr/usdImaging/usdVolImaging/tokens.h>
 
-#include "BKE_object.h"
+#include "BKE_volume.h"
 #include "DNA_volume_types.h"
+#include "BLI_index_range.hh"
 
 #include "blender_scene_delegate.h"
 #include "volume.h"
@@ -22,12 +28,19 @@ VolumeData::VolumeData(BlenderSceneDelegate *scene_delegate,
 void VolumeData::init()
 {
   ID_LOG(1, "");
-  scene_delegate_->GetRenderIndex().InsertRprim(
-      pxr::HdPrimTypeTokens->volume, scene_delegate_, prim_id);
+  write_transform();
 }
 
 void VolumeData::insert()
 {
+  ID_LOG(1, "");
+  scene_delegate_->GetRenderIndex().InsertRprim(
+      pxr::HdPrimTypeTokens->volume, scene_delegate_, prim_id);
+
+  for (auto &desc : volume_field_descriptors()) {
+    scene_delegate_->GetRenderIndex().InsertBprim(
+        desc.fieldPrimType, scene_delegate_, desc.fieldId);
+  }
 }
 
 void VolumeData::remove()
@@ -40,6 +53,25 @@ void VolumeData::update()
 
 pxr::VtValue VolumeData::get_data(pxr::SdfPath const &id, pxr::TfToken const &key) const
 {
+  Volume *volume = (Volume *)((Object *)this->id)->data;
+  Main *main = CTX_data_main(scene_delegate_->context);
+  BKE_volume_load(volume, main);
+  if (key == pxr::HdVolumeFieldSchemaTokens->filePath) {
+    auto path = BKE_volume_grids_frame_filepath(volume);
+    return pxr::VtValue(pxr::SdfAssetPath(path, path));
+  }
+  if (key == pxr::HdVolumeFieldSchemaTokens->fieldName) {
+    std::string name = id.GetName();
+    auto a = name.substr(name.find("_") + 1);
+    return pxr::VtValue(pxr::TfToken(name.substr(name.find("_") + 1)));
+  }
+  if (key == pxr::HdVolumeFieldSchemaTokens->fieldIndex) {
+    return pxr::VtValue(0);
+  }
+  if (key == pxr::UsdHydraTokens->textureMemory) {
+    return pxr::VtValue(0.0f);
+  }
+  BKE_volume_unload(volume);
   return pxr::VtValue();
 }
 
@@ -52,12 +84,30 @@ pxr::HdVolumeFieldDescriptorVector VolumeData::volume_field_descriptors() const
 {
   pxr::HdVolumeFieldDescriptorVector volume_field_descriptors;
   Volume *volume = (Volume *)((Object *)id)->data;
+  Main *main = CTX_data_main(scene_delegate_->context);
+  if (!BKE_volume_load(volume, main)) {
+    return pxr::HdVolumeFieldDescriptorVector();
+  }
 
-  //pxr::HdVolumeFieldDescriptor density = pxr::HdVolumeFieldDescriptor(pxr::TfToken("density"),)
-  //TfToken fieldName;
-  //TfToken fieldPrimType;
-  //SdfPath fieldId;
+  const int num_grids = BKE_volume_num_grids(volume);
+  if (!num_grids) {
+    return pxr::HdVolumeFieldDescriptorVector();
+  }
 
+  const std::string grid_path = BKE_volume_grids_frame_filepath(volume);
+
+  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);
+    
+    pxr::HdVolumeFieldDescriptor desc = pxr::HdVolumeFieldDescriptor(
+        pxr::TfToken(grid_name),
+        pxr::UsdVolImagingTokens->openvdbAsset,
+        prim_id.AppendElementString("field_" + grid_name));
+    volume_field_descriptors.push_back(desc);
+  }
+
+  BKE_volume_unload(volume);
   return volume_field_descriptors;
 }