Fix for Final Image Histogram debug mode not working on some hardware #7041

Author: FrancescoC-unity

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

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed vertex color mode Add name whicgh was misleading, renamed to AddSubstract.
 - Fixed screen space shadow when multiple lights cast shadows.
 - Fixed issue with dynamic resolution and low res transparency sampling garbage outside of the render target.
+- Fixed issue with Final Image Histogram displaying a flat histogram on certain GPUs and APIs.
 
 ## [10.8.0] - 2021-09-20
 

com.unity.render-pipelines.high-definition/Runtime/PostProcessing/PostProcessSystem.cs

@@ -1582,7 +1582,7 @@ internal DebugImageHistogramParameters PrepareDebugImageHistogramParameters(HDCa
             parameters.debugImageHistogramCS = m_Resources.shaders.debugImageHistogramCS;
             parameters.debugImageHistogramKernel = parameters.debugImageHistogramCS.FindKernel("KHistogramGen");
 
-            ValidateComputeBuffer(ref m_DebugImageHistogramBuffer, k_DebugImageHistogramBins * 4, sizeof(uint));
+            ValidateComputeBuffer(ref m_DebugImageHistogramBuffer, k_DebugImageHistogramBins, 4 * sizeof(uint));
             m_DebugImageHistogramBuffer.SetData(m_EmptyDebugImageHistogram);    // Clear the histogram
 
             parameters.imageHistogram = m_DebugImageHistogramBuffer;