Fix 2121_APV_Baking_Sky_Occlusion test: revert ref image change and use more reliable sampler than xor shift

The sky occlusion ref image was incorrectly updated for HDRP Test: 2121_APV_Baking_Sky_Occlusion.png.
What can be perceived on bottom right as an artifact is actually test the rendering layers feature for APV.

Author: yvain-raeymaekers

Packages/com.unity.render-pipelines.core/Editor/Lighting/ProbeVolume/ProbeGIBaking.RenderingLayers.cs

@@ -2,6 +2,7 @@
 using System.Runtime.InteropServices;
 using UnityEngine.Rendering.UnifiedRayTracing;
 using Unity.Collections;
+using UnityEngine.Rendering.Sampling;
 
 namespace UnityEngine.Rendering
 {
@@ -46,6 +47,7 @@ class DefaultRenderingLayer : RenderingLayerBaker
             static readonly int _ProbePositions = Shader.PropertyToID("_ProbePositions");
             static readonly int _LayerMasks = Shader.PropertyToID("_LayerMasks");
             static readonly int _RenderingLayerMasks = Shader.PropertyToID("_RenderingLayerMasks");
+            static readonly int _SobolBuffer = Shader.PropertyToID("_SobolMatricesBuffer");
 
             int batchIndex, batchCount;
             Vector4 regionMasks;
@@ -63,6 +65,7 @@ class DefaultRenderingLayer : RenderingLayerBaker
             AccelStructAdapter m_AccelerationStructure;
             GraphicsBuffer scratchBuffer;
             GraphicsBuffer probePositionsBuffer;
+            GraphicsBuffer sobolBuffer;
 
             public override ulong currentStep => (ulong)batchIndex;
             public override ulong stepCount => (ulong)batchCount;
@@ -92,12 +95,16 @@ public override void Initialize(ProbeVolumeBakingSet bakingSet, NativeArray<Vect
                 layerMaskBuffer = new GraphicsBuffer(GraphicsBuffer.Target.Structured, batchSize, Marshal.SizeOf<uint>());
                 scratchBuffer = RayTracingHelper.CreateScratchBufferForBuildAndDispatch(m_AccelerationStructure.GetAccelerationStructure(), s_TracingContext.shaderRL, (uint)batchSize, 1, 1);
 
+                int sobolBufferSize = (int)(SobolData.SobolDims * SobolData.SobolSize);
+                sobolBuffer = new GraphicsBuffer(GraphicsBuffer.Target.Structured, sobolBufferSize, Marshal.SizeOf<uint>());
+                sobolBuffer.SetData(SobolData.SobolMatrices);
+
                 cmd = new CommandBuffer();
                 m_AccelerationStructure.Build(cmd, ref scratchBuffer);
                 Graphics.ExecuteCommandBuffer(cmd);
                 cmd.Clear();
             }
-
+     
             static AccelStructAdapter BuildAccelerationStructure()
             {
                 var accelStruct = s_TracingContext.CreateAccelerationStructure();
@@ -115,6 +122,7 @@ static AccelStructAdapter BuildAccelerationStructure()
                         var matIndices = new uint[subMeshCount];
                         Array.Fill(matIndices, renderer.component.renderingLayerMask); // repurpose the material id as we don't need it here
                         var perSubMeshMask = new uint[subMeshCount];
+
                         Array.Fill(perSubMeshMask, GetInstanceMask(renderer.component.shadowCastingMode));
                         accelStruct.AddInstance(renderer.component.GetInstanceID(), renderer.component, perSubMeshMask, matIndices);
                     }
@@ -145,6 +153,7 @@ public override bool Step()
                 shader.SetVectorParam(cmd, _RenderingLayerMasks, regionMasks);
                 shader.SetBufferParam(cmd, _ProbePositions, probePositionsBuffer);
                 shader.SetBufferParam(cmd, _LayerMasks, layerMaskBuffer);
+                shader.SetBufferParam(cmd, _SobolBuffer, sobolBuffer);
 
                 shader.Dispatch(cmd, scratchBuffer, (uint)batchSize, 1, 1);
                 batchIndex++;
@@ -176,6 +185,7 @@ public override void Dispose()
                 scratchBuffer?.Dispose();
                 probePositionsBuffer.Dispose();
                 m_AccelerationStructure.Dispose();
+                sobolBuffer?.Dispose();
 
                 layerMaskBuffer.Dispose();
                 layerMask.Dispose();

Packages/com.unity.render-pipelines.core/Editor/Lighting/ProbeVolume/RenderingLayerMask/TraceRenderingLayerMask.hlsl

@@ -4,7 +4,7 @@
 #include "Packages/com.unity.rendering.light-transport/Runtime/UnifiedRayTracing/FetchGeometry.hlsl"
 #include "Packages/com.unity.rendering.light-transport/Runtime/UnifiedRayTracing/TraceRay.hlsl"
 
-#define QRNG_METHOD_RANDOM_XOR_SHIFT
+#define QRNG_METHOD_SOBOL
 #define SAMPLE_COUNT 32
 #define RAND_SAMPLES_PER_BOUNCE 2
 #include "Packages/com.unity.rendering.light-transport/Runtime/Sampling/QuasiRandom.hlsl"