source/blender/render/hydra/engine.cc

@@ -25,7 +25,7 @@ Engine::Engine(RenderEngine *bl_engine, const std::string &render_delegate_name)
   pxr::TF_PY_ALLOW_THREADS_IN_SCOPE();
   render_delegate_ = registry.CreateRenderDelegate(pxr::TfToken(render_delegate_name_));
 
-  /* Current USD (23.02) has limited support for Vulkan. To make it works USD should be built
+  /* 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 */
   if (GPU_backend_get_type() == GPU_BACKEND_VULKAN) {
     BLI_setenv("HGI_ENABLE_VULKAN", "1");

source/blender/render/hydra/preview_engine.cc

@@ -14,16 +14,16 @@ const double LIFETIME = 180.0;
 std::unique_ptr<PreviewEngine> PreviewEngine::instance_;
 
 PreviewEngine *PreviewEngine::get_instance(RenderEngine *bl_engine,
-                                           const std::string &render_delegate_id)
+                                           const std::string &render_delegate_name)
 {
   if (!instance_) {
-    instance_ = std::make_unique<PreviewEngine>(bl_engine, render_delegate_id);
+    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());
   }
-  instance_->update(bl_engine, render_delegate_id);
+  instance_->update(bl_engine, render_delegate_name);
 
   return instance_.get();
 }
@@ -96,10 +96,13 @@ double PreviewEngine::free_instance(uintptr_t uuid, void *user_data)
   return -1;
 }
 
-void PreviewEngine::update(RenderEngine *bl_engine, const std::string &render_delegate_id)
+void PreviewEngine::update(RenderEngine *bl_engine, const std::string &render_delegate_name)
 {
-  this->bl_engine_ = bl_engine;
+  bl_engine_ = bl_engine;
-  /* TODO: recreate render_delegate when render_delegate_id is changed */
+  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)

source/blender/render/hydra/preview_engine.h

@@ -12,7 +12,7 @@ class PreviewEngine : public FinalEngine {
   using FinalEngine::FinalEngine;
 
   static PreviewEngine *get_instance(RenderEngine *bl_engine,
-                                     const std::string &render_delegate_id);
+                                     const std::string &render_delegate_name);
   static void schedule_free();
 
   void sync(Depsgraph *depsgraph,
@@ -25,7 +25,7 @@ class PreviewEngine : public 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_id);
+  void update(RenderEngine *bl_engine, const std::string &render_delegate_name);
   void update_render_result(std::vector<float> &pixels);
 };
 

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

@@ -15,7 +15,7 @@ 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,
-                                           std::string render_delegate_name)
+                                           const std::string &render_delegate_name)
     : HdSceneDelegate(parent_index, delegate_id),
       engine_type(engine_type),
       render_delegate_name(render_delegate_name)
@@ -187,6 +187,11 @@ void BlenderSceneDelegate::clear()
   objects_.clear();
   instancers_.clear();
   materials_.clear();
+
+  depsgraph = nullptr;
+  context = nullptr;
+  scene = nullptr;
+  view3d = nullptr;
 }
 
 pxr::SdfPath BlenderSceneDelegate::prim_id(ID *id, const char *prefix) const
@@ -253,6 +258,8 @@ InstancerData *BlenderSceneDelegate::instancer_data(pxr::SdfPath const &id, bool
 {
   pxr::SdfPath p_id;
   if (child_id) {
+    /* Getting instancer path id from child Mesh instance (consist with 3 path elements) and
+     * Light instance (consist with 4 path elements) */
     int n = id.GetPathElementCount();
     if (n == 3) {
       p_id = id.GetParentPath();

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

@@ -30,7 +30,7 @@ class BlenderSceneDelegate : public pxr::HdSceneDelegate {
   BlenderSceneDelegate(pxr::HdRenderIndex *parent_index,
                        pxr::SdfPath const &delegate_id,
                        BlenderSceneDelegate::EngineType engine_type,
-                       std::string render_delegate_name);
+                       const std::string &render_delegate_name);
   ~BlenderSceneDelegate() override = default;
 
   /* Delegate methods */