[8.x.x Backport] Fix depth pyramid issues with dynamic resolution

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

@@ -70,6 +70,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed for area light not updating baked light result when modifying with gizmo.
 - Fixed issue with white flash when enabling SSR.
 - Fix inconsistencies with transparent motion vectors and opaque by allowing camera only transparent motion vectors.
+- Fixed issue with depth pyramid generation and dynamic resolution.
 
 ### Changed
 - Shadowmask and realtime reflection probe property are hide in Quality settings

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

@@ -4047,6 +4047,7 @@ void GenerateDepthPyramid(HDCamera hdCamera, CommandBuffer cmd, FullScreenDebugM
         {
             CopyDepthBufferIfNeeded(hdCamera, cmd);
 
+            m_SharedRTManager.GetDepthBufferMipChainInfo().ComputePackedMipChainInfo(new Vector2Int(hdCamera.actualWidth, hdCamera.actualHeight));
             int mipCount = m_SharedRTManager.GetDepthBufferMipChainInfo().mipLevelCount;
 
             using (new ProfilingScope(cmd, ProfilingSampler.Get(HDProfileId.DepthPyramid)))

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Utility/HDUtils.cs

@@ -508,6 +508,10 @@ public void Allocate()
             // This function is NOT fast, but it is illustrative, and can be optimized later.
             public void ComputePackedMipChainInfo(Vector2Int viewportSize)
             {
+                // No work needed.
+                if (viewportSize == mipLevelSizes[0])
+                    return;
+
                 textureSize = viewportSize;
                 mipLevelSizes[0] = viewportSize;
                 mipLevelOffsets[0] = Vector2Int.zero;