Fix volumetric fog in planar reflections

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

@@ -233,6 +233,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed some aliasing ussues with the volumetric clouds.
 - Fixed reflection probes being injected into the ray tracing light cluster even if not baked (case 1329083).
 - Fixed the double sided option moving when toggling it in the material UI (case 1328877).
+- Fixed volumetric fog in planar reflections.
 
 ### Changed
 - Changed Window/Render Pipeline/HD Render Pipeline Wizard to Window/Rendering/HDRP Wizard

com.unity.render-pipelines.high-definition/Runtime/Lighting/VolumetricLighting/VolumetricLighting.cs

@@ -429,6 +429,10 @@ GenerateMaxZParameters PrepareGenerateMaxZParameters(HDCamera hdCamera, HDUtils.
         {
             var parameters = new GenerateMaxZParameters();
             parameters.generateMaxZCS = defaultResources.shaders.maxZCS;
+            parameters.generateMaxZCS.shaderKeywords = null;
+            bool planarReflection = hdCamera.camera.cameraType == CameraType.Reflection && hdCamera.parentCamera != null;
+            CoreUtils.SetKeyword(parameters.generateMaxZCS, "PLANAR_OBLIQUE_DEPTH", planarReflection);
+
             parameters.maxZKernel = parameters.generateMaxZCS.FindKernel("ComputeMaxZ");
             parameters.maxZDownsampleKernel = parameters.generateMaxZCS.FindKernel("ComputeFinalMask");
             parameters.dilateMaxZKernel = parameters.generateMaxZCS.FindKernel("DilateMask");

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/RenderPass/GenerateMaxZ.compute

@@ -8,6 +8,7 @@
 #pragma kernel ComputeFinalMask FINAL_MASK=1
 #pragma kernel DilateMask DILATE_MASK=1
 
+#pragma multi_compile _ PLANAR_OBLIQUE_DEPTH
 
 // In some cases we might want to avoid stopping integrating volumetric even if > max distance if the gradient is very big.
 // Realistically, with the dilation step this was never seen as necessary.
@@ -48,14 +49,20 @@ groupshared float gs_maxDepth[GROUP_SIZE * GROUP_SIZE];
 
 RW_TEXTURE2D_X(float, _OutputTexture);
 
+
 float GetDepthToDownsample(uint2 pixCoord)
 {
     float deviceDepth = LoadCameraDepth(pixCoord);
     float outputDepth = 0;
+
     if (deviceDepth == UNITY_RAW_FAR_CLIP_VALUE)
         outputDepth = 1e10f;
     else
+#ifdef PLANAR_OBLIQUE_DEPTH
+        outputDepth = ComputeViewSpacePosition(float2(pixCoord) * _ScreenSize.zw, deviceDepth, UNITY_MATRIX_I_P).z;
+#else
         outputDepth = LinearEyeDepth(LoadCameraDepth(pixCoord), _ZBufferParams);
+#endif
 
     return outputDepth;
 }