Add ISceneRenderingListener for using scene information in renderer cache

Source/Engine/Level/Scene/SceneRendering.cpp

@@ -10,6 +10,23 @@
 #include "Engine/Profiler/ProfilerCPU.h"
 #endif
 
+ISceneRenderingListener::~ISceneRenderingListener()
+{
+    for (SceneRendering* scene : _scenes)
+    {
+        scene->_listeners.Remove(this);
+    }
+}
+
+void ISceneRenderingListener::ListenSceneRendering(SceneRendering* scene)
+{
+    if (!_scenes.Contains(scene))
+    {
+        _scenes.Add(scene);
+        scene->_listeners.Add(this);
+    }
+}
+
 void SceneRendering::Draw(RenderContext& renderContext)
 {
     auto& view = renderContext.View;
@@ -73,6 +90,12 @@ void SceneRendering::CollectPostFxVolumes(RenderContext& renderContext)
 
 void SceneRendering::Clear()
 {
+    for (auto* listener : _listeners)
+    {
+        listener->OnSceneRenderingClear(this);
+        listener->_scenes.Remove(this);
+    }
+    _listeners.Clear();
     Actors.Clear();
 #if USE_EDITOR
     PhysicsDebug.Clear();
@@ -95,6 +118,8 @@ int32 SceneRendering::AddActor(Actor* a)
     e.LayerMask = a->GetLayerMask();
     e.Bounds = a->GetSphere();
     e.NoCulling = a->_drawNoCulling;
+    for (auto* listener : _listeners)
+        listener->OnSceneRenderingAddActor(a);
     return key;
 }
 
@@ -104,6 +129,8 @@ void SceneRendering::UpdateActor(Actor* a, int32 key)
         return;
     auto& e = Actors[key];
     ASSERT_LOW_LAYER(a == e.Actor);
+    for (auto* listener : _listeners)
+        listener->OnSceneRenderingUpdateActor(a, e.Bounds);
     e.LayerMask = a->GetLayerMask();
     e.Bounds = a->GetSphere();
 }
@@ -114,6 +141,8 @@ void SceneRendering::RemoveActor(Actor* a, int32& key)
     {
         auto& e = Actors[key];
         ASSERT_LOW_LAYER(a == e.Actor);
+        for (auto* listener : _listeners)
+            listener->OnSceneRenderingRemoveActor(a);
         e.Actor = nullptr;
         e.LayerMask = 0;
     }

Source/Engine/Level/Scene/SceneRendering.h

@@ -8,6 +8,7 @@
 #include "Engine/Level/Actor.h"
 
 class SceneRenderTask;
+class SceneRendering;
 struct PostProcessSettings;
 struct RenderContext;
 struct RenderView;
@@ -32,6 +33,28 @@ public:
     virtual void Blend(PostProcessSettings& other, float weight) = 0;
 };
 
+/// <summary>
+/// Interface for objects to plug into Scene Rendering and listen for its evens such as static actors changes which are relevant for drawing cache.
+/// </summary>
+/// <seealso cref="SceneRendering"/>
+class FLAXENGINE_API ISceneRenderingListener
+{
+    friend SceneRendering;
+private:
+    Array<SceneRendering*, InlinedAllocation<8>> _scenes;
+public:
+    ~ISceneRenderingListener();
+
+    // Starts listening to the scene rendering events.
+    void ListenSceneRendering(SceneRendering* scene);
+
+    // Events called by Scene Rendering
+    virtual void OnSceneRenderingAddActor(Actor* a) = 0;
+    virtual void OnSceneRenderingUpdateActor(Actor* a, const BoundingSphere& prevBounds) = 0;
+    virtual void OnSceneRenderingRemoveActor(Actor* a) = 0;
+    virtual void OnSceneRenderingClear(SceneRendering* scene) = 0;
+};
+
 /// <summary>
 /// Scene rendering helper subsystem that boosts the level rendering by providing efficient objects cache and culling implementation.
 /// </summary>
@@ -59,6 +82,10 @@ private:
     Array<Actor*> ViewportIcons;
 #endif
 
+    // Listener - some rendering systems cache state of the scene (eg. in RenderBuffers::CustomBuffer), this extensions allows those systems to invalidate cache and handle scene changes
+    friend ISceneRenderingListener;
+    Array<ISceneRenderingListener*, InlinedAllocation<8>> _listeners;
+
 public:
     /// <summary>
     /// Draws the scene. Performs the optimized actors culling and draw calls submission for the current render pass (defined by the render view).