scripts/modules/bpy_hydra.py

@@ -21,10 +21,15 @@ class CustomHydraRenderEngine(HydraRenderEngine):
 
         bpy_hydra.register_plugins(["/path/to/plugin")])
 
-    def get_delegate_settings(self, engine_type):
+    def get_sync_settings(self, engine_type):
         return {
-            'setting1': 1,
-            'setting2': "2",
+            'MaterialXFilenameKey': "MaterialXFilename",
+        }
+
+    def get_render_settings(self, engine_type):
+        return {
+            'enableTinyPrimCulling': True,
+            'maxLights': 8,
         }
 ```
 """
@@ -73,27 +78,52 @@ class HydraRenderEngine(bpy.types.RenderEngine):
     def unregister(cls):
         pass
 
-    def get_delegate_settings(self, engine_type):
+    def get_sync_settings(self, engine_type):
+        """
+        Provide settings for Blender scene delegate. Available settings:
+            `MaterialXFilenameKey` - if provided then MaterialX file will be provided directly to render delegate
+                                     without converting to HdMaterialNetwork
+        """
+        return {}
+
+    def get_render_settings(self, engine_type):
+        """
+        Provide render settings for render delegate. List of settings should be available in render delegate
+        documentation or in `pxr.UsdImagingGL.Engine.GetRendererSettingsList()`
+        """
         return {}
 
     # final render
     def update(self, data, depsgraph):
         engine_type = 'PREVIEW' if self.is_preview else 'FINAL'
         self.engine_ptr = _bpy_hydra.engine_create(self.as_pointer(), engine_type, self.delegate_id)
-        delegate_settings = self.get_delegate_settings(engine_type)
-        _bpy_hydra.engine_sync(self.engine_ptr, depsgraph.as_pointer(), bpy.context.as_pointer(), delegate_settings)
+
+        for key, val in self.get_sync_settings(engine_type).items():
+            _bpy_hydra.engine_set_sync_setting(self.engine_ptr, key, val)
+
+        _bpy_hydra.engine_sync(self.engine_ptr, depsgraph.as_pointer(), bpy.context.as_pointer())
 
     def render(self, depsgraph):
-        if self.engine_ptr:
-            _bpy_hydra.engine_render(self.engine_ptr, depsgraph.as_pointer())
+        if not self.engine_ptr:
+            return
+
+        for key, val in self.get_render_settings('PREVIEW' if self.is_preview else 'FINAL').items():
+            _bpy_hydra.engine_set_render_setting(self.engine_ptr, key, val)
+
+        _bpy_hydra.engine_render(self.engine_ptr, depsgraph.as_pointer())
 
     # viewport render
     def view_update(self, context, depsgraph):
         if not self.engine_ptr:
             self.engine_ptr = _bpy_hydra.engine_create(self.as_pointer(), 'VIEWPORT', self.delegate_id)
 
-        delegate_settings = self.get_delegate_settings('VIEWPORT')
-        _bpy_hydra.engine_sync(self.engine_ptr, depsgraph.as_pointer(), context.as_pointer(), delegate_settings)
+        for key, val in self.get_sync_settings('VIEWPORT').items():
+            _bpy_hydra.engine_set_sync_setting(self.engine_ptr, key, val)
+
+        _bpy_hydra.engine_sync(self.engine_ptr, depsgraph.as_pointer(), context.as_pointer())
+
+        for key, val in self.get_render_settings('VIEWPORT').items():
+            _bpy_hydra.engine_set_render_setting(self.engine_ptr, key, val)
 
     def view_draw(self, context, depsgraph):
         if not self.engine_ptr:

source/blender/render/hydra/engine.cc

@@ -18,12 +18,12 @@ namespace blender::render::hydra {
 CLG_LOGREF_DECLARE_GLOBAL(LOG_RENDER_HYDRA, "render.hydra");
 
 Engine::Engine(RenderEngine *bl_engine, const std::string &render_delegate_name)
-    : bl_engine_(bl_engine), render_delegate_name_(render_delegate_name)
+    : render_delegate_name(render_delegate_name), bl_engine_(bl_engine)
 {
   pxr::HdRendererPluginRegistry &registry = pxr::HdRendererPluginRegistry::GetInstance();
 
   pxr::TF_PY_ALLOW_THREADS_IN_SCOPE();
-  render_delegate_ = registry.CreateRenderDelegate(pxr::TfToken(render_delegate_name_));
+  render_delegate_ = registry.CreateRenderDelegate(pxr::TfToken(render_delegate_name));
 
   /* USD has limited support for Vulkan. To make it works USD should be built
    * with PXR_ENABLE_VULKAN_SUPPORT=TRUE which is not possible now */
@@ -43,9 +43,11 @@ Engine::Engine(RenderEngine *bl_engine, const std::string &render_delegate_name)
   render_index_.reset(pxr::HdRenderIndex::New(render_delegate_.Get(), hd_drivers));
   free_camera_delegate_ = std::make_unique<pxr::HdxFreeCameraSceneDelegate>(
       render_index_.get(), pxr::SdfPath::AbsoluteRootPath().AppendElementString("freeCamera"));
+  scene_delegate_ = std::make_unique<BlenderSceneDelegate>(
+      render_index_.get(), pxr::SdfPath::AbsoluteRootPath().AppendElementString("scene"), this);
   render_task_delegate_ = std::make_unique<RenderTaskDelegate>(
       render_index_.get(), pxr::SdfPath::AbsoluteRootPath().AppendElementString("renderTask"));
-  if (render_delegate_name_ == "HdStormRendererPlugin") {
+  if (render_delegate_name == "HdStormRendererPlugin") {
     simple_light_task_delegate_ = std::make_unique<SimpleLightTaskDelegate>(
         render_index_.get(),
         pxr::SdfPath::AbsoluteRootPath().AppendElementString("simpleLightTask"));
@@ -54,6 +56,21 @@ Engine::Engine(RenderEngine *bl_engine, const std::string &render_delegate_name)
   engine_ = std::make_unique<pxr::HdEngine>();
 }
 
+void Engine::sync(Depsgraph *depsgraph, bContext *context)
+{
+  scene_delegate_->populate(depsgraph, context);
+}
+
+void Engine::set_sync_setting(const std::string &key, const pxr::VtValue &val)
+{
+  scene_delegate_->set_setting(key, val);
+}
+
+void Engine::set_render_setting(const std::string &key, const pxr::VtValue &val)
+{
+  render_delegate_->SetRenderSetting(pxr::TfToken(key), val);
+}
+
 float Engine::renderer_percent_done()
 {
   pxr::VtDictionary render_stats = render_delegate_->GetRenderStats();

source/blender/render/hydra/engine.h

@@ -28,16 +28,18 @@ class Engine {
   Engine(RenderEngine *bl_engine, const std::string &render_delegate_name);
   virtual ~Engine() = default;
 
-  virtual void sync(Depsgraph *depsgraph,
-                    bContext *context,
-                    pxr::HdRenderSettingsMap &render_settings) = 0;
+  void sync(Depsgraph *depsgraph, bContext *context);
   virtual void render(Depsgraph *depsgraph) = 0;
 
+  void set_sync_setting(const std::string &key, const pxr::VtValue &val);
+  void set_render_setting(const std::string &key, const pxr::VtValue &val);
+
+  std::string render_delegate_name;
+
  protected:
   float renderer_percent_done();
 
   RenderEngine *bl_engine_;
-  std::string render_delegate_name_;
 
   /* The order is important due to deletion order */
   pxr::HgiUniquePtr hgi_;

source/blender/render/hydra/final_engine.cc

@@ -13,22 +13,6 @@
 
 namespace blender::render::hydra {
 
-void FinalEngine::sync(Depsgraph *depsgraph,
-                       bContext *context,
-                       pxr::HdRenderSettingsMap &render_settings)
-{
-  scene_delegate_ = std::make_unique<BlenderSceneDelegate>(
-      render_index_.get(),
-      pxr::SdfPath::AbsoluteRootPath().AppendElementString("scene"),
-      BlenderSceneDelegate::EngineType::FINAL,
-      render_delegate_name_);
-  scene_delegate_->populate(depsgraph, context);
-
-  for (auto const &setting : render_settings) {
-    render_delegate_->SetRenderSetting(setting.first, setting.second);
-  }
-}
-
 void FinalEngine::render(Depsgraph *depsgraph)
 {
   prepare_for_render(depsgraph);

source/blender/render/hydra/final_engine.h

@@ -11,10 +11,7 @@ class FinalEngine : public Engine {
  public:
   using Engine::Engine;
 
-  virtual void sync(Depsgraph *depsgraph,
-                    bContext *context,
-                    pxr::HdRenderSettingsMap &render_settings) override;
-  virtual void render(Depsgraph *b_depsgraph) override;
+  void render(Depsgraph *b_depsgraph) override;
 
  protected:
   void update_render_result();

source/blender/render/hydra/preview_engine.cc

@@ -13,46 +13,36 @@ const double LIFETIME = 180.0;
 
 std::unique_ptr<PreviewEngine> PreviewEngine::instance_;
 
-PreviewEngine *PreviewEngine::get_instance(RenderEngine *bl_engine,
-                                           const std::string &render_delegate_name)
+PreviewEngine *PreviewEngine::create(RenderEngine *bl_engine,
+                                     const std::string &render_delegate_name)
 {
   if (!instance_) {
     instance_ = std::make_unique<PreviewEngine>(bl_engine, render_delegate_name);
   }
-  if (BLI_timer_is_registered((uintptr_t)instance_.get())) {
-    /* Unregister timer while PreviewEngine is working */
-    BLI_timer_unregister((uintptr_t)instance_.get());
+  else if (instance_->render_delegate_name != render_delegate_name) {
+    instance_->render_delegate_->Stop();
+    instance_ = std::make_unique<PreviewEngine>(bl_engine, render_delegate_name);
+  }
+  else {
+    instance_->bl_engine_ = bl_engine;
+  }
+
+  instance_->scene_delegate_->clear();
+
+  if (BLI_timer_is_registered((uintptr_t)&instance_)) {
+    /* Unregister timer while PreviewEngine is working */
+    BLI_timer_unregister((uintptr_t)&instance_);
   }
-  instance_->update(bl_engine, render_delegate_name);
 
   return instance_.get();
 }
 
-void PreviewEngine::schedule_free()
+void PreviewEngine::free()
 {
   instance_->render_delegate_->Stop();
 
   /* Register timer for schedule free PreviewEngine instance */
-  BLI_timer_register((uintptr_t)instance_.get(), free_instance, nullptr, nullptr, LIFETIME, true);
-}
-
-void PreviewEngine::sync(Depsgraph *depsgraph,
-                         bContext *context,
-                         pxr::HdRenderSettingsMap &render_settings)
-{
-  if (!scene_delegate_) {
-    scene_delegate_ = std::make_unique<BlenderSceneDelegate>(
-        render_index_.get(),
-        pxr::SdfPath::AbsoluteRootPath().AppendElementString("scene"),
-        BlenderSceneDelegate::EngineType::PREVIEW,
-        render_delegate_name_);
-  }
-  scene_delegate_->clear();
-  scene_delegate_->populate(depsgraph, context);
-
-  for (auto const &setting : render_settings) {
-    render_delegate_->SetRenderSetting(setting.first, setting.second);
-  }
+  BLI_timer_register((uintptr_t)&instance_, free_instance, nullptr, nullptr, LIFETIME, true);
 }
 
 void PreviewEngine::render(Depsgraph *depsgraph)
@@ -96,15 +86,6 @@ double PreviewEngine::free_instance(uintptr_t uuid, void *user_data)
   return -1;
 }
 
-void PreviewEngine::update(RenderEngine *bl_engine, const std::string &render_delegate_name)
-{
-  bl_engine_ = bl_engine;
-  if (render_delegate_name != render_delegate_name_) {
-    render_delegate_->Stop();
-    instance_.reset(new PreviewEngine(bl_engine, render_delegate_name));
-  }
-}
-
 void PreviewEngine::update_render_result(std::vector<float> &pixels)
 {
   RenderResult *result = RE_engine_begin_result(

source/blender/render/hydra/preview_engine.h

@@ -9,24 +9,19 @@ namespace blender::render::hydra {
 
 class PreviewEngine : public FinalEngine {
  public:
-  using FinalEngine::FinalEngine;
+  static PreviewEngine *create(RenderEngine *bl_engine, const std::string &render_delegate_name);
+  static void free();
 
-  static PreviewEngine *get_instance(RenderEngine *bl_engine,
-                                     const std::string &render_delegate_name);
-  static void schedule_free();
-
-  void sync(Depsgraph *depsgraph,
-            bContext *context,
-            pxr::HdRenderSettingsMap &render_settings) override;
   void render(Depsgraph *depsgraph) override;
 
  private:
-  /* Singleton class instance */
+  using FinalEngine::FinalEngine;
   static double free_instance(uintptr_t uuid, void *user_data);
-  static std::unique_ptr<PreviewEngine> instance_;
 
-  void update(RenderEngine *bl_engine, const std::string &render_delegate_name);
   void update_render_result(std::vector<float> &pixels);
+
+  /* Singleton class instance */
+  static std::unique_ptr<PreviewEngine> instance_;
 };
 
 }  // namespace blender::render::hydra

source/blender/render/hydra/python.cc

@@ -111,7 +111,7 @@ static PyObject *engine_create_func(PyObject * /*self*/, PyObject *args)
     engine = new ViewportEngine(bl_engine, render_delegate_id);
   }
   else if (STREQ(engine_type, "PREVIEW")) {
-    engine = PreviewEngine::get_instance(bl_engine, render_delegate_id);
+    engine = PreviewEngine::create(bl_engine, render_delegate_id);
   }
   else {
     if (bl_engine->type->flag & RE_USE_GPU_CONTEXT) {
@@ -123,7 +123,6 @@ static PyObject *engine_create_func(PyObject * /*self*/, PyObject *args)
   }
 
   CLOG_INFO(LOG_RENDER_HYDRA, 2, "Engine %016llx %s", engine, engine_type);
-
   return PyLong_FromVoidPtr(engine);
 }
 
@@ -137,7 +136,7 @@ static PyObject *engine_free_func(PyObject * /*self*/, PyObject *args)
   Engine *engine = (Engine *)PyLong_AsVoidPtr(pyengine);
   PreviewEngine *preview_engine = dynamic_cast<PreviewEngine *>(engine);
   if (preview_engine) {
-    PreviewEngine::schedule_free();
+    PreviewEngine::free();
   }
   else {
     delete engine;
@@ -149,8 +148,8 @@ static PyObject *engine_free_func(PyObject * /*self*/, PyObject *args)
 
 static PyObject *engine_sync_func(PyObject * /*self*/, PyObject *args)
 {
-  PyObject *pyengine, *pydepsgraph, *pycontext, *pysettings;
-  if (!PyArg_ParseTuple(args, "OOOO", &pyengine, &pydepsgraph, &pycontext, &pysettings)) {
+  PyObject *pyengine, *pydepsgraph, *pycontext;
+  if (!PyArg_ParseTuple(args, "OOO", &pyengine, &pydepsgraph, &pycontext)) {
     Py_RETURN_NONE;
   }
 
@@ -158,29 +157,7 @@ static PyObject *engine_sync_func(PyObject * /*self*/, PyObject *args)
   Depsgraph *depsgraph = (Depsgraph *)PyLong_AsVoidPtr(pydepsgraph);
   bContext *context = (bContext *)PyLong_AsVoidPtr(pycontext);
 
-  pxr::HdRenderSettingsMap settings;
-  PyObject *pyiter = PyObject_GetIter(pysettings);
-  if (pyiter) {
-    PyObject *pykey, *pyval;
-    while (pykey = PyIter_Next(pyiter)) {
-      pxr::TfToken key(PyUnicode_AsUTF8(pykey));
-      pyval = PyDict_GetItem(pysettings, pykey);
-
-      if (PyLong_Check(pyval)) {
-        settings[key] = PyLong_AsLong(pyval);
-      }
-      else if (PyFloat_Check(pyval)) {
-        settings[key] = PyFloat_AsDouble(pyval);
-      }
-      else if (PyUnicode_Check(pyval)) {
-        settings[key] = PyUnicode_AsUTF8(pyval);
-      }
-      Py_DECREF(pykey);
-    }
-    Py_DECREF(pyiter);
-  }
-
-  engine->sync(depsgraph, context, settings);
+  engine->sync(depsgraph, context);
 
   CLOG_INFO(LOG_RENDER_HYDRA, 2, "Engine %016llx", engine);
   Py_RETURN_NONE;
@@ -226,6 +203,54 @@ static PyObject *engine_view_draw_func(PyObject * /*self*/, PyObject *args)
   Py_RETURN_NONE;
 }
 
+static pxr::VtValue get_setting_val(PyObject *pyval)
+{
+  pxr::VtValue val;
+  if (PyBool_Check(pyval)) {
+    val = Py_IsTrue(pyval);
+  }
+  else if (PyLong_Check(pyval)) {
+    val = PyLong_AsLong(pyval);
+  }
+  else if (PyFloat_Check(pyval)) {
+    val = PyFloat_AsDouble(pyval);
+  }
+  else if (PyUnicode_Check(pyval)) {
+    val = std::string(PyUnicode_AsUTF8(pyval));
+  }
+  return val;
+}
+
+static PyObject *engine_set_sync_setting_func(PyObject * /*self*/, PyObject *args)
+{
+  PyObject *pyengine, *pyval;
+  char *key;
+  if (!PyArg_ParseTuple(args, "OsO", &pyengine, &key, &pyval)) {
+    Py_RETURN_NONE;
+  }
+
+  Engine *engine = (Engine *)PyLong_AsVoidPtr(pyengine);
+  engine->set_sync_setting(key, get_setting_val(pyval));
+
+  CLOG_INFO(LOG_RENDER_HYDRA, 3, "Engine %016llx: %s", engine, key);
+  Py_RETURN_NONE;
+}
+
+static PyObject *engine_set_render_setting_func(PyObject * /*self*/, PyObject *args)
+{
+  PyObject *pyengine, *pyval;
+  char *key;
+  if (!PyArg_ParseTuple(args, "OsO", &pyengine, &key, &pyval)) {
+    Py_RETURN_NONE;
+  }
+
+  Engine *engine = (Engine *)PyLong_AsVoidPtr(pyengine);
+  engine->set_render_setting(key, get_setting_val(pyval));
+
+  CLOG_INFO(LOG_RENDER_HYDRA, 3, "Engine %016llx: %s", engine, key);
+  Py_RETURN_NONE;
+}
+
 static PyMethodDef methods[] = {
     {"init", init_func, METH_VARARGS, ""},
     {"register_plugins", register_plugins_func, METH_VARARGS, ""},
@@ -236,6 +261,8 @@ static PyMethodDef methods[] = {
     {"engine_sync", engine_sync_func, METH_VARARGS, ""},
     {"engine_render", engine_render_func, METH_VARARGS, ""},
     {"engine_view_draw", engine_view_draw_func, METH_VARARGS, ""},
+    {"engine_set_sync_setting", engine_set_sync_setting_func, METH_VARARGS, ""},
+    {"engine_set_render_setting", engine_set_render_setting_func, METH_VARARGS, ""},
 
     {NULL, NULL, 0, NULL},
 };

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

@@ -14,11 +14,8 @@ CLG_LOGREF_DECLARE_GLOBAL(LOG_RENDER_HYDRA_SCENE, "render.hydra.scene");
 
 BlenderSceneDelegate::BlenderSceneDelegate(pxr::HdRenderIndex *parent_index,
                                            pxr::SdfPath const &delegate_id,
-                                           BlenderSceneDelegate::EngineType engine_type,
-                                           const std::string &render_delegate_name)
-    : HdSceneDelegate(parent_index, delegate_id),
-      engine_type(engine_type),
-      render_delegate_name(render_delegate_name)
+                                           Engine *engine)
+    : HdSceneDelegate(parent_index, delegate_id), engine(engine)
 {
 }
 
@@ -206,6 +203,13 @@ void BlenderSceneDelegate::clear()
   view3d = nullptr;
 }
 
+void BlenderSceneDelegate::set_setting(const std::string &key, const pxr::VtValue &val)
+{
+  if (key == "MaterialXFilenameKey") {
+    settings.mx_filename_key = pxr::TfToken(val.Get<std::string>());
+  }
+}
+
 pxr::SdfPath BlenderSceneDelegate::prim_id(ID *id, const char *prefix) const
 {
   /* Making id of object in form like <prefix>_<pointer in 16 hex digits format> */
@@ -376,8 +380,8 @@ void BlenderSceneDelegate::check_updates()
   DEGIDIterData data = {0};
   data.graph = depsgraph;
   data.only_updated = true;
-  ITER_BEGIN (
-      DEG_iterator_ids_begin, DEG_iterator_ids_next, DEG_iterator_ids_end, &data, ID *, id) {
+  ITER_BEGIN (DEG_iterator_ids_begin, DEG_iterator_ids_next, DEG_iterator_ids_end, &data, ID *, id)
+  {
 
     CLOG_INFO(LOG_RENDER_HYDRA_SCENE,
               2,
@@ -451,7 +455,8 @@ void BlenderSceneDelegate::add_new_objects()
               DEG_iterator_objects_end,
               &data,
               Object *,
-              object) {
+              object)
+  {
 
     update_objects(object);
     update_instancers(object);
@@ -476,7 +481,8 @@ void BlenderSceneDelegate::remove_unused_objects()
               DEG_iterator_objects_end,
               &data,
               Object *,
-              object) {
+              object)
+  {
     if (ObjectData::is_supported(object)) {
       available_objects.insert(object_prim_id(object).GetName());
     }
@@ -554,7 +560,8 @@ void BlenderSceneDelegate::update_visibility()
               DEG_iterator_objects_end,
               &data,
               Object *,
-              object) {
+              object)
+  {
 
     if (!object_data(object_prim_id(object))) {
       update_objects(object);

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

@@ -21,18 +21,21 @@ namespace blender::render::hydra {
 
 extern struct CLG_LogRef *LOG_RENDER_HYDRA_SCENE;
 
+class Engine;
+
 class BlenderSceneDelegate : public pxr::HdSceneDelegate {
   friend ObjectData;   /* has access to instances */
   friend MeshData;     /* has access to materials */
   friend MaterialData; /* has access to objects and instancers */
 
  public:
-  enum class EngineType { VIEWPORT = 1, FINAL, PREVIEW };
+  struct Settings {
+    pxr::TfToken mx_filename_key;
+  };
 
   BlenderSceneDelegate(pxr::HdRenderIndex *parent_index,
                        pxr::SdfPath const &delegate_id,
-                       BlenderSceneDelegate::EngineType engine_type,
-                       const std::string &render_delegate_name);
+                       Engine *engine);
   ~BlenderSceneDelegate() override = default;
 
   /* Delegate methods */
@@ -55,14 +58,14 @@ class BlenderSceneDelegate : public pxr::HdSceneDelegate {
 
   void populate(Depsgraph *depsgraph, bContext *context);
   void clear();
+  void set_setting(const std::string &key, const pxr::VtValue &val);
 
-  EngineType engine_type;
   Depsgraph *depsgraph = nullptr;
   bContext *context = nullptr;
   View3D *view3d = nullptr;
   Scene *scene = nullptr;
-
-  std::string render_delegate_name;
+  Engine *engine;
+  Settings settings;
 
  private:
   pxr::SdfPath prim_id(ID *id, const char *prefix) const;

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

@@ -66,7 +66,8 @@ void InstancerData::update()
   Object *object = (Object *)id;
   if (id->recalc & ID_RECALC_GEOMETRY ||
       (object->data && ((ID *)object->data)->recalc & ID_RECALC_GEOMETRY) ||
-      id->recalc & ID_RECALC_TRANSFORM) {
+      id->recalc & ID_RECALC_TRANSFORM)
+  {
     set_instances();
     scene_delegate_->GetRenderIndex().GetChangeTracker().MarkInstancerDirty(
         prim_id, pxr::HdChangeTracker::AllDirty);
@@ -174,7 +175,8 @@ void InstancerData::check_update(Object *object)
   if (l_it != light_instances_.end()) {
     Object *obj = (Object *)l_it->second.data->id;
     if (obj->id.recalc & (ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY) ||
-        ((ID *)obj->data)->recalc & ID_RECALC_GEOMETRY) {
+        ((ID *)obj->data)->recalc & ID_RECALC_GEOMETRY)
+    {
       set_instances();
     }
     return;

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

@@ -14,6 +14,7 @@
 #include "RNA_blender_cpp.h"
 #include "bpy_rna.h"
 
+#include "../engine.h"
 #include "blender_scene_delegate.h"
 #include "material.h"
 #include "mtlx_hydra_adapter.h"
@@ -31,8 +32,65 @@ void MaterialData::init()
 {
   ID_LOG(2, "");
   double_sided = (((Material *)id)->blend_flag & MA_BL_CULL_BACKFACE) == 0;
-  material_network_map_ = pxr::VtValue();
 
+  export_mtlx();
+  if (scene_delegate_->settings.mx_filename_key.IsEmpty()) {
+    write_material_network_map();
+  }
+}
+
+void MaterialData::insert()
+{
+  ID_LOG(2, "");
+  scene_delegate_->GetRenderIndex().InsertSprim(
+      pxr::HdPrimTypeTokens->material, scene_delegate_, prim_id);
+}
+
+void MaterialData::remove()
+{
+  CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 2, "%s", prim_id.GetText());
+  scene_delegate_->GetRenderIndex().RemoveSprim(pxr::HdPrimTypeTokens->material, prim_id);
+}
+
+void MaterialData::update()
+{
+  ID_LOG(2, "");
+  bool prev_double_sided = double_sided;
+  init();
+  scene_delegate_->GetRenderIndex().GetChangeTracker().MarkSprimDirty(prim_id,
+                                                                      pxr::HdMaterial::AllDirty);
+  if (prev_double_sided != double_sided) {
+    for (auto &it : scene_delegate_->objects_) {
+      MeshData *m_data = dynamic_cast<MeshData *>(it.second.get());
+      if (m_data) {
+        m_data->update_double_sided(this);
+      }
+    }
+    for (auto &it : scene_delegate_->instancers_) {
+      it.second->update_double_sided(this);
+    }
+  }
+}
+
+pxr::VtValue MaterialData::get_data(pxr::TfToken const &key) const
+{
+  pxr::VtValue ret;
+  if (key == scene_delegate_->settings.mx_filename_key) {
+    if (!mtlx_path_.GetResolvedPath().empty()) {
+      ret = mtlx_path_;
+    }
+    ID_LOG(3, "%s", key.GetText());
+  }
+  return ret;
+}
+
+pxr::VtValue MaterialData::get_material_resource() const
+{
+  return material_network_map_;
+}
+
+void MaterialData::export_mtlx()
+{
   /* Call of python function hydra.export_mtlx() */
 
   PyGILState_STATE gstate;
@@ -87,71 +145,25 @@ void MaterialData::init()
 
   mtlx_path_ = pxr::SdfAssetPath(path, path);
   ID_LOG(2, "mtlx=%s", mtlx_path_.GetResolvedPath().c_str());
+}
 
-  /* Calculate material network map */
-  if (!path.empty()) {
-    pxr::HdRenderDelegate *render_delegate = scene_delegate_->GetRenderIndex().GetRenderDelegate();
-    pxr::TfTokenVector shader_source_types = render_delegate->GetShaderSourceTypes();
-    pxr::TfTokenVector render_contexts = render_delegate->GetMaterialRenderContexts();
-
-    pxr::HdMaterialNetworkMap network_map;
-    hdmtlx_convert_to_materialnetworkmap(path, shader_source_types, render_contexts, &network_map);
-
-    material_network_map_ = network_map;
-  }
-  else {
+void MaterialData::write_material_network_map()
+{
+  ID_LOG(2, "");
+  if (mtlx_path_.GetResolvedPath().empty()) {
     material_network_map_ = pxr::VtValue();
+    return;
   }
-}
 
-void MaterialData::insert()
-{
-  ID_LOG(2, "");
-  scene_delegate_->GetRenderIndex().InsertSprim(
-      pxr::HdPrimTypeTokens->material, scene_delegate_, prim_id);
-}
+  pxr::HdRenderDelegate *render_delegate = scene_delegate_->GetRenderIndex().GetRenderDelegate();
+  pxr::TfTokenVector shader_source_types = render_delegate->GetShaderSourceTypes();
+  pxr::TfTokenVector render_contexts = render_delegate->GetMaterialRenderContexts();
 
-void MaterialData::remove()
-{
-  CLOG_INFO(LOG_RENDER_HYDRA_SCENE, 2, "%s", prim_id.GetText());
-  scene_delegate_->GetRenderIndex().RemoveSprim(pxr::HdPrimTypeTokens->material, prim_id);
-}
+  pxr::HdMaterialNetworkMap network_map;
+  hdmtlx_convert_to_materialnetworkmap(
+      mtlx_path_.GetResolvedPath(), shader_source_types, render_contexts, &network_map);
 
-void MaterialData::update()
-{
-  ID_LOG(2, "");
-  bool prev_double_sided = double_sided;
-  init();
-  scene_delegate_->GetRenderIndex().GetChangeTracker().MarkSprimDirty(prim_id,
-                                                                      pxr::HdMaterial::AllDirty);
-  if (prev_double_sided != double_sided) {
-    for (auto &it : scene_delegate_->objects_) {
-      MeshData *m_data = dynamic_cast<MeshData *>(it.second.get());
-      if (m_data) {
-        m_data->update_double_sided(this);
-      }
-    }
-    for (auto &it : scene_delegate_->instancers_) {
-      it.second->update_double_sided(this);
-    }
-  }
-}
-
-pxr::VtValue MaterialData::get_data(pxr::TfToken const &key) const
-{
-  pxr::VtValue ret;
-  if (key.GetString() == "MaterialXFilename") {
-    if (!mtlx_path_.GetResolvedPath().empty()) {
-      ret = mtlx_path_;
-    }
-    ID_LOG(3, "%s", key.GetText());
-  }
-  return ret;
-}
-
-pxr::VtValue MaterialData::get_material_resource() const
-{
-  return material_network_map_;
+  material_network_map_ = network_map;
 }
 
 }  // namespace blender::render::hydra

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

@@ -30,6 +30,9 @@ class MaterialData : public IdData {
   bool double_sided = true;
 
  private:
+  void export_mtlx();
+  void write_material_network_map();
+
   pxr::SdfAssetPath mtlx_path_;
   pxr::VtValue material_network_map_;
 };

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

@@ -27,7 +27,8 @@ void MeshData::init()
 
   Object *object = (Object *)id;
   if (object->type == OB_MESH && object->mode == OB_MODE_OBJECT &&
-      BLI_listbase_is_empty(&object->modifiers)) {
+      BLI_listbase_is_empty(&object->modifiers))
+  {
     write_mesh((Mesh *)object->data);
   }
   else {

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

@@ -19,6 +19,7 @@
 #include "BLI_path_util.h"
 #include "NOD_shader.h"
 
+#include "../engine.h"
 #include "blender_scene_delegate.h"
 #include "image.h"
 #include "world.h"
@@ -143,7 +144,7 @@ void WorldData::write_transform()
   transform = pxr::GfMatrix4d(pxr::GfRotation(pxr::GfVec3d(1.0, 0.0, 0.0), -90), pxr::GfVec3d());
 
   /* TODO : do this check via RenderSettings*/
-  if (scene_delegate_->render_delegate_name == "HdRprPlugin") {
+  if (scene_delegate_->engine->render_delegate_name == "HdRprPlugin") {
     transform *= pxr::GfMatrix4d(pxr::GfRotation(pxr::GfVec3d(1.0, 0.0, 0.0), -180),
                                  pxr::GfVec3d());
     transform *= pxr::GfMatrix4d(pxr::GfRotation(pxr::GfVec3d(0.0, 0.0, 1.0), 90.0),

source/blender/render/hydra/viewport_engine.cc

@@ -217,24 +217,6 @@ void DrawTexture::free()
   texture_ = nullptr;
 }
 
-void ViewportEngine::sync(Depsgraph *depsgraph,
-                          bContext *context,
-                          pxr::HdRenderSettingsMap &render_settings)
-{
-  if (!scene_delegate_) {
-    scene_delegate_ = std::make_unique<BlenderSceneDelegate>(
-        render_index_.get(),
-        pxr::SdfPath::AbsoluteRootPath().AppendElementString("scene"),
-        BlenderSceneDelegate::EngineType::VIEWPORT,
-        render_delegate_name_);
-  }
-  scene_delegate_->populate(depsgraph, context);
-
-  for (auto const &setting : render_settings) {
-    render_delegate_->SetRenderSetting(setting.first, setting.second);
-  }
-}
-
 void ViewportEngine::render(Depsgraph *depsgraph)
 {
   /* Empty function */

source/blender/render/hydra/viewport_engine.h

@@ -34,9 +34,6 @@ class ViewportEngine : public Engine {
  public:
   using Engine::Engine;
 
-  void sync(Depsgraph *depsgraph,
-            bContext *context,
-            pxr::HdRenderSettingsMap &render_settings) override;
   void render(Depsgraph *depsgraph) override;
   void render(Depsgraph *depsgraph, bContext *context);