From b3d18f3b0e4722f1deb894bf67191d439fa32d4e Mon Sep 17 00:00:00 2001
From: Wojciech Figat <wojtek@figat.pl>
Date: Thu, 21 Apr 2022 12:39:27 +0200
Subject: [PATCH] Improve `StaticModel` to register for Scene Rendering once
 the model has any LOD streamed-in

---
 Source/Engine/Level/Actors/StaticModel.cpp   | 59 ++++++++++++++++++--
 Source/Engine/Level/Actors/StaticModel.h     |  4 ++
 Source/Engine/Level/Scene/SceneRendering.cpp |  6 ++
 Source/Engine/Level/Scene/SceneRendering.h   |  2 +
 4 files changed, 67 insertions(+), 4 deletions(-)

diff --git a/Source/Engine/Level/Actors/StaticModel.cpp b/Source/Engine/Level/Actors/StaticModel.cpp
index a32512b1b..41cb38515 100644
--- a/Source/Engine/Level/Actors/StaticModel.cpp
+++ b/Source/Engine/Level/Actors/StaticModel.cpp
@@ -163,20 +163,46 @@ void StaticModel::RemoveVertexColors()
 
 void StaticModel::OnModelChanged()
 {
+    if (_residencyChangedModel)
+    {
+        _residencyChangedModel = nullptr;
+        Model->ResidencyChanged.Unbind<StaticModel, &StaticModel::OnModelResidencyChanged>(this);
+    }
     RemoveVertexColors();
     Entries.Release();
-
     if (Model && !Model->IsLoaded())
-    {
         UpdateBounds();
-    }
+    else if (!Model && _sceneRenderingKey != -1)
+        GetSceneRendering()->RemoveActor(this, _sceneRenderingKey);
 }
 
 void StaticModel::OnModelLoaded()
 {
     Entries.SetupIfInvalid(Model);
-
     UpdateBounds();
+    if (_sceneRenderingKey == -1 && _scene)
+    {
+        // Register for rendering but once the model has any LOD loaded
+        if (Model->GetLoadedLODs() == 0)
+        {
+            _residencyChangedModel = Model;
+            Model->ResidencyChanged.Bind<StaticModel, &StaticModel::OnModelResidencyChanged>(this);
+        }
+        else
+        {
+            _sceneRenderingKey = GetSceneRendering()->AddActor(this);
+        }
+    }
+}
+
+void StaticModel::OnModelResidencyChanged()
+{
+    if (_sceneRenderingKey == -1 && _scene && Model && Model->GetLoadedLODs() > 0)
+    {
+        _sceneRenderingKey = GetSceneRendering()->AddActor(this);
+        _residencyChangedModel = nullptr;
+        Model->ResidencyChanged.Unbind<StaticModel, &StaticModel::OnModelResidencyChanged>(this);
+    }
 }
 
 void StaticModel::UpdateBounds()
@@ -488,3 +514,28 @@ void StaticModel::OnTransformChanged()
     _transform.GetWorld(_world);
     UpdateBounds();
 }
+
+void StaticModel::OnEnable()
+{
+    if (_scene && Model && Model->IsLoaded() && Model->GetLoadedLODs() > 0 && _sceneRenderingKey == -1)
+        _sceneRenderingKey = GetSceneRendering()->AddActor(this);
+
+    // Skip ModelInstanceActor (add to SceneRendering manually)
+    Actor::OnEnable();
+}
+
+void StaticModel::OnDisable()
+{
+    // Skip ModelInstanceActor (add to SceneRendering manually)
+    Actor::OnDisable();
+
+    if (_sceneRenderingKey != -1)
+    {
+        GetSceneRendering()->RemoveActor(this, _sceneRenderingKey);
+    }
+    else if (_residencyChangedModel)
+    {
+        _residencyChangedModel = nullptr;
+        Model->ResidencyChanged.Unbind<StaticModel, &StaticModel::OnModelResidencyChanged>(this);
+    }
+}
diff --git a/Source/Engine/Level/Actors/StaticModel.h b/Source/Engine/Level/Actors/StaticModel.h
index 60f0355bf..db0ece1a6 100644
--- a/Source/Engine/Level/Actors/StaticModel.h
+++ b/Source/Engine/Level/Actors/StaticModel.h
@@ -25,6 +25,7 @@ private:
     byte _vertexColorsCount;
     Array<Color32> _vertexColorsData[MODEL_MAX_LODS];
     GPUBuffer* _vertexColorsBuffer[MODEL_MAX_LODS];
+    Model* _residencyChangedModel = nullptr;
 
 public:
 
@@ -182,6 +183,7 @@ private:
 
     void OnModelChanged();
     void OnModelLoaded();
+    void OnModelResidencyChanged();
     void UpdateBounds();
 
 public:
@@ -199,4 +201,6 @@ protected:
 
     // [ModelInstanceActor]
     void OnTransformChanged() override;
+    void OnEnable() override;
+    void OnDisable() override;
 };
diff --git a/Source/Engine/Level/Scene/SceneRendering.cpp b/Source/Engine/Level/Scene/SceneRendering.cpp
index c29db6bee..3090fd798 100644
--- a/Source/Engine/Level/Scene/SceneRendering.cpp
+++ b/Source/Engine/Level/Scene/SceneRendering.cpp
@@ -6,6 +6,7 @@
 #include "Engine/Graphics/RenderTask.h"
 #include "Engine/Graphics/RenderView.h"
 #include "Engine/Renderer/RenderList.h"
+#include "Engine/Threading/Threading.h"
 #if SCENE_RENDERING_USE_PROFILER
 #include "Engine/Profiler/ProfilerCPU.h"
 #endif
@@ -29,6 +30,7 @@ void ISceneRenderingListener::ListenSceneRendering(SceneRendering* scene)
 
 void SceneRendering::Draw(RenderContext& renderContext)
 {
+    ScopeLock lock(Locker);
     auto& view = renderContext.View;
     const BoundingFrustum frustum = view.CullingFrustum;
     renderContext.List->Scenes.Add(this);
@@ -90,6 +92,7 @@ void SceneRendering::CollectPostFxVolumes(RenderContext& renderContext)
 
 void SceneRendering::Clear()
 {
+    ScopeLock lock(Locker);
     for (auto* listener : _listeners)
     {
         listener->OnSceneRenderingClear(this);
@@ -104,6 +107,7 @@ void SceneRendering::Clear()
 
 int32 SceneRendering::AddActor(Actor* a)
 {
+    ScopeLock lock(Locker);
     int32 key = 0;
     // TODO: track removedCount and skip searching for free entry if there is none
     for (; key < Actors.Count(); key++)
@@ -125,6 +129,7 @@ int32 SceneRendering::AddActor(Actor* a)
 
 void SceneRendering::UpdateActor(Actor* a, int32 key)
 {
+    ScopeLock lock(Locker);
     if (Actors.IsEmpty())
         return;
     auto& e = Actors[key];
@@ -137,6 +142,7 @@ void SceneRendering::UpdateActor(Actor* a, int32 key)
 
 void SceneRendering::RemoveActor(Actor* a, int32& key)
 {
+    ScopeLock lock(Locker);
     if (Actors.HasItems())
     {
         auto& e = Actors[key];
diff --git a/Source/Engine/Level/Scene/SceneRendering.h b/Source/Engine/Level/Scene/SceneRendering.h
index 160a89510..9aed3e3b7 100644
--- a/Source/Engine/Level/Scene/SceneRendering.h
+++ b/Source/Engine/Level/Scene/SceneRendering.h
@@ -6,6 +6,7 @@
 #include "Engine/Core/Collections/Array.h"
 #include "Engine/Core/Math/BoundingSphere.h"
 #include "Engine/Level/Actor.h"
+#include "Engine/Platform/CriticalSection.h"
 
 class SceneRenderTask;
 class SceneRendering;
@@ -75,6 +76,7 @@ public:
 
     Array<DrawActor> Actors;
     Array<IPostFxSettingsProvider*> PostFxProviders;
+    CriticalSection Locker;
 
 private:
 #if USE_EDITOR