Fix white flash on camera cuts with volumetric

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

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed lights shadow frustum near and far planes.
 - Fixed various issues with non-temporal SSAO and rendergraph.
 - Fix screen being over-exposed when changing very different skies.
+- White flashes on camera cuts on volumetric fog.
 
 ### Changed
 - Removed the material pass probe volumes evaluation mode.

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Camera/HDCamera.cs

@@ -83,6 +83,8 @@ public struct ViewConstants
         /// <summary>Volumetric history buffer state.</summary>
         public bool                 volumetricHistoryIsValid = false;
 
+        internal int                volumetricValidFrames = 0;
+
         /// <summary>Width actually used for rendering after dynamic resolution and XR is applied.</summary>
         public int                  actualWidth { get; private set; }
         /// <summary>Height actually used for rendering after dynamic resolution and XR is applied.</summary>
@@ -129,6 +131,7 @@ public void Reset()
             cameraFrameCount = 0;
             resetPostProcessingHistory = true;
             volumetricHistoryIsValid = false;
+            volumetricValidFrames = 0;
             colorPyramidHistoryIsValid = false;
         }
 

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/HDRenderPipeline.LightLoop.cs

@@ -742,8 +742,10 @@ TextureHandle VolumetricLightingPass(RenderGraph renderGraph, HDCamera hdCamera,
                                 FilterVolumetricLighting(data.parameters, data.lightingBuffer, ctx.cmd);
                         });
 
-                    if (parameters.enableReprojection)
+                    if (parameters.enableReprojection && hdCamera.volumetricValidFrames > 1)
                         hdCamera.volumetricHistoryIsValid = true; // For the next frame..
+                    else
+                        hdCamera.volumetricValidFrames++;
 
                     return passData.lightingBuffer;
                 }