Improve MSAA color resolve when very different samples are merged together

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -125,6 +125,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Optimized Grain and sRGB Dithering.
 - On platforms that allow it skip the first mip of the depth pyramid and compute it alongside the depth buffer used for low res transparents.
 - When trying to install the local configuration package, if another one is already present the user is now asked whether they want to keep it or not.
+- Improved MSAA color resolve to fix issues when very bright and very dark samples are resolved together.
 
 ## [10.0.0] - 2019-06-10
 

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/RenderPass/MSAA/ColorResolve.shader

@@ -33,11 +33,41 @@ Shader "Hidden/HDRP/ColorResolve"
             return output;
         }
 
+        float ResolveWeight(float4 color, float totalSampleCount)
+        {
+            const float boxFilterWeight = rcp(totalSampleCount);
+            float toneMapWeight = rcp(1.0f + Luminance(color.xyz));
+
+            return boxFilterWeight * toneMapWeight;
+        }
+
+        float InverseToneMapWeight(float4 color)
+        {
+            return rcp(1.0f - Luminance(color.xyz));
+        }
+
         float4 LoadColorTextureMS(float2 pixelCoords, uint sampleIndex)
         {
             return LOAD_TEXTURE2D_X_MSAA(_ColorTextureMS, pixelCoords, sampleIndex);
         }
 
+        float4 Resolve(Varyings input, uint sampleCount)
+        {
+            UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
+            int2 pixelCoords = int2(input.texcoord);
+
+            float4 finalVal = 0;
+            for (int i = 0; i < sampleCount; ++i)
+            {
+                float4 currSample = (LoadColorTextureMS(pixelCoords, i));
+                finalVal += currSample * ResolveWeight(currSample, sampleCount);
+            }
+
+            finalVal.xyz *= InverseToneMapWeight(finalVal);
+
+            return float4(finalVal.rgb, 1.0f);
+        }
+
         float4 Frag1X(Varyings input) : SV_Target
         {
             UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
@@ -47,28 +77,19 @@ Shader "Hidden/HDRP/ColorResolve"
 
         float4 Frag2X(Varyings input) : SV_Target
         {
-            UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
-            int2 pixelCoords = int2(input.texcoord);
-            return FastTonemapInvert((FastTonemap(LoadColorTextureMS(pixelCoords, 0)) + FastTonemap(LoadColorTextureMS(pixelCoords, 1))) * 0.5f);
+            return Resolve(input, 2);
         }
 
         float4 Frag4X(Varyings input) : SV_Target
         {
-            UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
-            int2 pixelCoords = int2(input.texcoord);
-            return FastTonemapInvert((FastTonemap(LoadColorTextureMS(pixelCoords, 0)) + FastTonemap(LoadColorTextureMS(pixelCoords, 1))
-                                    + FastTonemap(LoadColorTextureMS(pixelCoords, 2)) + FastTonemap(LoadColorTextureMS(pixelCoords, 3))) * 0.25f);
+            return Resolve(input, 4);
         }
 
         float4 Frag8X(Varyings input) : SV_Target
         {
-            UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
-            int2 pixelCoords = int2(input.texcoord);
-            return FastTonemapInvert((FastTonemap(LoadColorTextureMS(pixelCoords, 0)) + FastTonemap(LoadColorTextureMS(pixelCoords, 1))
-                                    + FastTonemap(LoadColorTextureMS(pixelCoords, 2)) + FastTonemap(LoadColorTextureMS(pixelCoords, 3))
-                                    + FastTonemap(LoadColorTextureMS(pixelCoords, 4)) + FastTonemap(LoadColorTextureMS(pixelCoords, 5))
-                                    + FastTonemap(LoadColorTextureMS(pixelCoords, 6)) + FastTonemap(LoadColorTextureMS(pixelCoords, 7))) * 0.125f);
+            return Resolve(input, 8);
         }
+
     ENDHLSL
     SubShader
     {