[Backport 7.x.x] Fixed error Maximum allowed thread group count is 65535 when resolution is very high

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

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed Custom Post Processes affecting preview cameras.
 - Fixed serialization issue with matcap scale intensity.
 - Fixed XR shadows culling
+- Fixed error Maximum allowed thread group count is 65535 when resolution is very high. 
 
 ### Changed
 - Removed XRSystemTests. The GC verification is now done during playmode tests (case 1285012).

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

@@ -3126,9 +3126,27 @@ void ClearLightList(HDCamera camera, CommandBuffer cmd, ComputeBuffer bufferToCl
             var kernel = cs.FindKernel("ClearList");
 
             cmd.SetComputeBufferParam(cs, kernel, HDShaderIDs._LightListToClear, bufferToClear);
-            cmd.SetComputeIntParam(cs, HDShaderIDs._LightListEntries, bufferToClear.count);
+            Vector2 countAndOffset = new Vector2Int(bufferToClear.count, 0);
 
             int groupSize = 64;
+            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(cs, HDShaderIDs._LightListEntriesAndOffset, countAndOffset);
+
+                int currGroupCount = Math.Min(maxAllowedGroups, totalNumberOfGroupsNeeded);
+
+                cmd.DispatchCompute(cs, kernel, currGroupCount, 1, 1);
+
+                totalNumberOfGroupsNeeded -= currGroupCount;
+                i++;
+            }
+
             cmd.DispatchCompute(cs, kernel, (bufferToClear.count + groupSize - 1) / groupSize, 1, 1);
         }
 

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

@@ -172,7 +172,7 @@ 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 _MousePixelCoord = Shader.PropertyToID("_MousePixelCoord");