From 2ad9c7f4d5aa3215504cdb6702e4239f97c89697 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Tue, 24 Sep 2024 23:01:13 +0200
Subject: [PATCH] Fix Skybox rendering regression

#2943
---
 Source/Engine/Graphics/Materials/IMaterial.h  |  2 ++
 .../Graphics/Materials/MaterialShader.cpp     | 21 +++++++++++++++++++
 Source/Engine/Level/Actors/Skybox.cpp         |  1 +
 Source/Engine/Renderer/RenderList.cpp         |  2 ++
 Source/Engine/Renderer/RenderList.h           |  5 +++++
 5 files changed, 31 insertions(+)

diff --git a/Source/Engine/Graphics/Materials/IMaterial.h b/Source/Engine/Graphics/Materials/IMaterial.h
index 90d44897e..ba0e2acae 100644
--- a/Source/Engine/Graphics/Materials/IMaterial.h
+++ b/Source/Engine/Graphics/Materials/IMaterial.h
@@ -166,6 +166,8 @@ public:
 
         // Binds the shared per-view constant buffer at slot 1 (see ViewData in MaterialCommon.hlsl)
         void BindViewData();
+        // Binds the shared per-draw constant buffer at slot 2 (see DrawData in MaterialCommon.hlsl)
+        void BindDrawData();
     };
 
     /// <summary>
diff --git a/Source/Engine/Graphics/Materials/MaterialShader.cpp b/Source/Engine/Graphics/Materials/MaterialShader.cpp
index fe1d1db2a..63faaf300 100644
--- a/Source/Engine/Graphics/Materials/MaterialShader.cpp
+++ b/Source/Engine/Graphics/Materials/MaterialShader.cpp
@@ -84,6 +84,27 @@ void IMaterial::BindParameters::BindViewData()
     GPUContext->BindCB(1, PerViewConstants);
 }
 
+void IMaterial::BindParameters::BindDrawData()
+{
+    // Write draw call to the object buffer
+    auto& objectBuffer = RenderContext.List->TempObjectBuffer;
+    objectBuffer.Clear();
+    ShaderObjectData objData;
+    objData.Store(*DrawCall);
+    objectBuffer.Write(objData);
+    objectBuffer.Flush(GPUContext);
+    ObjectBuffer = objectBuffer.GetBuffer()->View();
+
+    // Setup data
+    MaterialShaderDataPerDraw perDraw;
+    perDraw.DrawPadding = Float3::Zero;
+    perDraw.DrawObjectIndex = 0;
+
+    // Update constants
+    GPUContext->UpdateCB(PerDrawConstants, &perDraw);
+    GPUContext->BindCB(2, PerDrawConstants);
+}
+
 GPUPipelineState* MaterialShader::PipelineStateCache::InitPS(CullMode mode, bool wireframe)
 {
     Desc.CullMode = mode;
diff --git a/Source/Engine/Level/Actors/Skybox.cpp b/Source/Engine/Level/Actors/Skybox.cpp
index 51b288c42..9077f4e39 100644
--- a/Source/Engine/Level/Actors/Skybox.cpp
+++ b/Source/Engine/Level/Actors/Skybox.cpp
@@ -111,6 +111,7 @@ void Skybox::ApplySky(GPUContext* context, RenderContext& renderContext, const M
     drawCall.PerInstanceRandom = GetPerInstanceRandom();
     MaterialBase::BindParameters bindParams(context, renderContext, drawCall);
     bindParams.BindViewData();
+    bindParams.BindDrawData();
 
     // Check if use custom material
     if (CustomMaterial)
diff --git a/Source/Engine/Renderer/RenderList.cpp b/Source/Engine/Renderer/RenderList.cpp
index 93a254c21..69032a2b7 100644
--- a/Source/Engine/Renderer/RenderList.cpp
+++ b/Source/Engine/Renderer/RenderList.cpp
@@ -443,6 +443,7 @@ RenderList::RenderList(const SpawnParams& params)
     , Fog(nullptr)
     , Blendable(32)
     , ObjectBuffer(0, PixelFormat::R32G32B32A32_Float, false, TEXT("Object Bufffer"))
+    , TempObjectBuffer(0, PixelFormat::R32G32B32A32_Float, false, TEXT("Object Bufffer"))
     , _instanceBuffer(0, sizeof(ShaderObjectDrawInstanceData), TEXT("Instance Buffer"))
 {
 }
@@ -477,6 +478,7 @@ void RenderList::Clear()
     Blendable.Clear();
     _instanceBuffer.Clear();
     ObjectBuffer.Clear();
+    TempObjectBuffer.Clear();
 }
 
 struct PackedSortKey
diff --git a/Source/Engine/Renderer/RenderList.h b/Source/Engine/Renderer/RenderList.h
index aa484fceb..43e295aa9 100644
--- a/Source/Engine/Renderer/RenderList.h
+++ b/Source/Engine/Renderer/RenderList.h
@@ -419,6 +419,11 @@ public:
     /// </summary>
     DynamicTypedBuffer ObjectBuffer;
 
+    /// <summary>
+    /// Temporary objects buffer that contains ShaderObjectData for each DrawCall reused during scene rendering (eg. by skybox).
+    /// </summary>
+    DynamicTypedBuffer TempObjectBuffer;
+
 private:
     DynamicVertexBuffer _instanceBuffer;