Fixed error Maximum allowed thread group count is 65535 when resolution is very high.

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

@@ -122,6 +122,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed Light skin not properly applied on the LookDev when switching from Dark Skin (case 1278802)
 - Fixed accumulation on DX11
 - Fixed issue with screen space UI not drawing on the graphics compositor (case 1279272).
+- Fixed error Maximum allowed thread group count is 65535 when resolution is very high. 
 
 ### Changed
 - Preparation pass for RTSSShadows to be supported by render graph.

com.unity.render-pipelines.high-definition/Runtime/Lighting/LightLoop/ClearLightLists.compute

@@ -1,11 +1,14 @@
 #pragma kernel ClearList
 
 RWStructuredBuffer<uint>  _LightListToClear;
-int _LightListEntries;
+int2 _LightListEntriesAndOffset;
+
+#define _LightListEntries (uint)_LightListEntriesAndOffset.x
+#define _LightListOffset  (uint)_LightListEntriesAndOffset.y
 
 [numthreads(64, 1, 1)]
 void ClearList(uint3 id : SV_DispatchThreadID)
 {
-    if (id.x < (uint)_LightListEntries)
-        _LightListToClear[id.x] = 0;
+    if ((id.x + _LightListOffset) < (uint)_LightListEntries)
+        _LightListToClear[id.x + _LightListOffset] = 0;
 }

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

@@ -3059,10 +3059,26 @@ BuildGPULightListResources PrepareBuildGPULightListResources(TileAndClusterData
         static void ClearLightList(in BuildGPULightListParameters parameters, CommandBuffer cmd, ComputeBuffer bufferToClear)
         {
             cmd.SetComputeBufferParam(parameters.clearLightListCS, parameters.clearLightListKernel, HDShaderIDs._LightListToClear, bufferToClear);
-            cmd.SetComputeIntParam(parameters.clearLightListCS, HDShaderIDs._LightListEntries, bufferToClear.count);
+            Vector2 countAndOffset = new Vector2Int(bufferToClear.count, 0);
 
             int groupSize = 64;
-            cmd.DispatchCompute(parameters.clearLightListCS, parameters.clearLightListKernel, (bufferToClear.count + groupSize - 1) / groupSize, 1, 1);
+            int totalNumberOfGroupsNeeded = (bufferToClear.count + groupSize - 1) / groupSize;
+
+            const int maxAllowedGroups = 65535;
+            // On higher resolutions we might end up with more than 65535 group which is not allowed, so we need to to have multiple dispatches.
+            int i = 0;
+            while(totalNumberOfGroupsNeeded > 0)
+            {
+                countAndOffset.y = maxAllowedGroups * i;                
+                cmd.SetComputeVectorParam(parameters.clearLightListCS, HDShaderIDs._LightListEntriesAndOffset, countAndOffset);
+
+                int currGroupCount = Math.Min(maxAllowedGroups, totalNumberOfGroupsNeeded);
+
+                cmd.DispatchCompute(parameters.clearLightListCS, parameters.clearLightListKernel, currGroupCount, 1, 1);
+
+                totalNumberOfGroupsNeeded -= currGroupCount;
+                i++;
+            }
         }
 
         static void ClearLightLists(    in BuildGPULightListParameters parameters,

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

@@ -127,7 +127,7 @@ static class HDShaderIDs
         public static readonly int g_vLayeredOffsetsBuffer = Shader.PropertyToID("g_vLayeredOffsetsBuffer");
 
         public static readonly int _LightListToClear = Shader.PropertyToID("_LightListToClear");
-        public static readonly int _LightListEntries = Shader.PropertyToID("_LightListEntries");
+        public static readonly int _LightListEntriesAndOffset = Shader.PropertyToID("_LightListEntriesAndOffset");
 
         public static readonly int _ViewTilesFlags = Shader.PropertyToID("_ViewTilesFlags");
         public static readonly int _ClusterDebugMode = Shader.PropertyToID("_ClusterDebugMode");