From ca935f4f08e53bb8ecbf5008f8408f751ce4eb4e Mon Sep 17 00:00:00 2001
From: Wojciech Figat <wojtek@figat.pl>
Date: Thu, 21 Apr 2022 12:40:23 +0200
Subject: [PATCH] Improve Global SDF static chunks cache to track SDF textures
 streaming

---
 .../Renderer/GlobalSignDistanceFieldPass.cpp  | 32 +++++++++++++++++++
 .../Renderer/GlobalSurfaceAtlasPass.cpp       |  1 +
 2 files changed, 33 insertions(+)

diff --git a/Source/Engine/Renderer/GlobalSignDistanceFieldPass.cpp b/Source/Engine/Renderer/GlobalSignDistanceFieldPass.cpp
index c4df8e611..f53e10511 100644
--- a/Source/Engine/Renderer/GlobalSignDistanceFieldPass.cpp
+++ b/Source/Engine/Renderer/GlobalSignDistanceFieldPass.cpp
@@ -164,8 +164,32 @@ class GlobalSignDistanceFieldCustomBuffer : public RenderBuffers::CustomBuffer,
 public:
     CascadeData Cascades[4];
     HashSet<ScriptingTypeHandle> ObjectTypes;
+    HashSet<GPUTexture*> SDFTextures;
     GlobalSignDistanceFieldPass::BindingData Result;
 
+    void OnSDFTextureDeleted(ScriptingObject* object)
+    {
+        auto* texture = (GPUTexture*)object;
+        if (SDFTextures.Remove(texture))
+        {
+            texture->Deleted.Unbind<GlobalSignDistanceFieldCustomBuffer, &GlobalSignDistanceFieldCustomBuffer::OnSDFTextureDeleted>(this);
+            texture->ResidentMipsChanged.Unbind<GlobalSignDistanceFieldCustomBuffer, &GlobalSignDistanceFieldCustomBuffer::OnSDFTextureResidentMipsChanged>(this);
+        }
+    }
+
+    void OnSDFTextureResidentMipsChanged(GPUTexture* texture)
+    {
+        // Stop tracking texture streaming once it gets fully loaded
+        if (texture->ResidentMipLevels() == texture->MipLevels())
+        {
+            OnSDFTextureDeleted(texture);
+
+            // Clear static chunks cache
+            for (auto& cascade : Cascades)
+                cascade.StaticChunks.Clear();
+        }
+    }
+
     FORCE_INLINE void OnSceneRenderingDirty(const BoundingBox& objectBounds)
     {
         for (auto& cascade : Cascades)
@@ -763,4 +787,12 @@ void GlobalSignDistanceFieldPass::RasterizeModelSDF(Actor* actor, const ModelBas
             }
         }
     }
+
+    // Track streaming for SDF textures used in static chunks to invalidate cache
+    if (!dynamic && sdf.Texture->ResidentMipLevels() != sdf.Texture->MipLevels() && !_sdfData->SDFTextures.Contains(sdf.Texture))
+    {
+        sdf.Texture->Deleted.Bind<GlobalSignDistanceFieldCustomBuffer, &GlobalSignDistanceFieldCustomBuffer::OnSDFTextureDeleted>(_sdfData);
+        sdf.Texture->ResidentMipsChanged.Bind<GlobalSignDistanceFieldCustomBuffer, &GlobalSignDistanceFieldCustomBuffer::OnSDFTextureResidentMipsChanged>(_sdfData);
+        _sdfData->SDFTextures.Add(sdf.Texture);
+    }
 }
diff --git a/Source/Engine/Renderer/GlobalSurfaceAtlasPass.cpp b/Source/Engine/Renderer/GlobalSurfaceAtlasPass.cpp
index b7a8148de..755fb6660 100644
--- a/Source/Engine/Renderer/GlobalSurfaceAtlasPass.cpp
+++ b/Source/Engine/Renderer/GlobalSurfaceAtlasPass.cpp
@@ -371,6 +371,7 @@ bool GlobalSurfaceAtlasPass::Render(RenderContext& renderContext, GPUContext* co
         const float distanceScalingStart = 2000.0f; // Distance from camera at which the tiles resolution starts to be scaled down
         const float distanceScalingEnd = 5000.0f; // Distance from camera at which the tiles resolution end to be scaled down
         const float distanceScaling = 0.1f; // The scale for tiles at distanceScalingEnd and further away
+        // TODO: add DetailsScale param to adjust quality of scene details in Global Surface Atlas
         static_assert(GLOBAL_SURFACE_ATLAS_TILE_PADDING < minTileResolution, "Invalid tile size configuration.");
         for (auto* scene : renderContext.List->Scenes)
         {