[2022.3][VFX] Split rendering batches for exposed meshes

Non trivial backport of [this PR](https://github.cds.internal.unity3d.com/unity/unity/pull/43927) When we allowed using exposed objects with instancing, we missed one case, using a exposed mesh with mesh particles. The fix contains 2 parts: - Identifying which CPU expressions can split instancing batches. Currently just mesh and submeshMask, but easy to add more - Supporting indirect draw rendering with different meshes To test, just expose a mesh and plug it directly into the mesh slot of a particle mesh output. Then, create many instances and use different meshes for some instances.
Unity-Technologies · Jun 27, 2024 · eefd1d2 · eefd1d2
1 parent 63913f6
commit eefd1d2
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Showing 7 changed files with 82 additions and 14 deletions.
diff --git a/Packages/com.unity.visualeffectgraph/Editor/Compiler/VFXGraphCompiledData.cs b/Packages/com.unity.visualeffectgraph/Editor/Compiler/VFXGraphCompiledData.cs
@@ -22,6 +22,7 @@ struct VFXContextCompiledData
         public VFXExpressionMapper gpuMapper;
         public VFXUniformMapper uniformMapper;
         public VFXSGInputs SGInputs;
+        public List<uint> instancingSplitValues;
         public ReadOnlyDictionary<VFXExpression, Type> graphicsBufferUsage;
         public VFXMapping[] parameters;
         public (VFXSlot slot, VFXData data)[] linkedEventOut;
@@ -1102,6 +1103,7 @@ public void Compile(VFXCompilationMode compilationMode, bool forceShaderValidati
                     contextData.cpuMapper = cpuMapper;
                     contextData.parameters = context.additionalMappings.ToArray();
                     contextData.linkedEventOut = ComputeEventListFromSlot(context.allLinkedOutputSlot).ToArray();
+                    contextData.instancingSplitValues = context.CreateInstancingSplitValues(m_ExpressionGraph);
                     contextToCompiledData[context] = contextData;
                 }
 

diff --git a/Packages/com.unity.visualeffectgraph/Editor/Data/VFXDataParticle.cs b/Packages/com.unity.visualeffectgraph/Editor/Data/VFXDataParticle.cs
@@ -962,7 +962,6 @@ public override void FillDescs(
             for (int i = 0; i < m_Contexts.Count; ++i)
             {
                 var temporaryBufferMappings = new List<VFXMappingTemporary>();
-                var instanceSplitDescValues = new List<uint>();
 
                 var context = m_Contexts[i];
                 if (!contextToCompiledData.TryGetValue(context, out var contextData))
@@ -1113,14 +1112,15 @@ public override void FillDescs(
                     bufferMappings.Add(new VFXMapping($"eventListOut_{prefix}", gpuTarget));
                 }
 
+                var instancingSplitDescValues = contextData.instancingSplitValues;
                 uniformMappings.Clear();
 
                 foreach (var buffer in contextData.uniformMapper.buffers)
                 {
                     int index = expressionGraph.GetFlattenedIndex(buffer);
                     if (!buffer.IsAny(VFXExpression.Flags.Constant | VFXExpression.Flags.Foldable))
                     {
-                        instanceSplitDescValues.Add((uint)index);
+                        instancingSplitDescValues.Add((uint)index);
                     }
                     var name = contextData.uniformMapper.GetName(buffer);
                     uniformMappings.Add(new VFXMapping(name, index));
@@ -1130,7 +1130,7 @@ public override void FillDescs(
                     int index = expressionGraph.GetFlattenedIndex(texture);
                     if (!texture.IsAny(VFXExpression.Flags.Constant | VFXExpression.Flags.Foldable))
                     {
-                        instanceSplitDescValues.Add((uint)index);
+                        instancingSplitDescValues.Add((uint)index);
                     }
                     // TODO At the moment issue all names sharing the same texture as different texture slots. This is not optimized as it required more texture binding than necessary
                     foreach (var name in contextData.uniformMapper.GetNames(texture))
@@ -1155,17 +1155,19 @@ public override void FillDescs(
                 taskDesc.values = uniformMappings.OrderBy(mapping => mapping.index).ToArray();
                 taskDesc.parameters = cpuMappings.Concat(contextData.parameters).Concat(additionalParameters).ToArray();
                 taskDesc.shaderSourceIndex = contextToCompiledData[context].indexInShaderSource;
-                taskDesc.instanceSplitIndex = AddInstanceSplitDesc(instanceSplitDescs, instanceSplitDescValues);
+                taskDesc.instanceSplitIndex = AddInstanceSplitDesc(instanceSplitDescs, instancingSplitDescValues);
                 taskDesc.model = context;
 
-                if (context is IVFXMultiMeshOutput) // If the context is a multi mesh output, split and patch task desc into several tasks
+                if (context is IVFXMultiMeshOutput multiMeshOutput && multiMeshOutput.meshCount > 0) // If the context is a multi mesh output, split and patch task desc into several tasks
                 {
-                    var multiMeshOutput = (IVFXMultiMeshOutput)context;
                     for (int j = (int)multiMeshOutput.meshCount - 1; j >= 0; --j) // Back to front to be consistent with LOD and alpha
                     {
                         VFXEditorTaskDesc singleMeshTaskDesc = taskDesc;
                         singleMeshTaskDesc.parameters = VFXMultiMeshHelper.PatchCPUMapping(taskDesc.parameters, multiMeshOutput.meshCount, j).ToArray();
                         singleMeshTaskDesc.buffers = VFXMultiMeshHelper.PatchBufferMapping(taskDesc.buffers, j).ToArray();
+                        var instancingSplitDescValuesMesh = new List<uint>(instancingSplitDescValues);
+                        VFXMultiMeshHelper.PatchInstancingSplitValues(instancingSplitDescValuesMesh, expressionGraph, context.inputSlots, multiMeshOutput.meshCount, j);
+                        singleMeshTaskDesc.instanceSplitIndex = AddInstanceSplitDesc(instanceSplitDescs, instancingSplitDescValuesMesh);
                         taskDescs.Add(singleMeshTaskDesc);
                     }
                 }

diff --git a/Packages/com.unity.visualeffectgraph/Editor/Models/Contexts/Implementations/VFXMeshOutput.cs b/Packages/com.unity.visualeffectgraph/Editor/Models/Contexts/Implementations/VFXMeshOutput.cs
@@ -158,5 +158,27 @@ internal override void GenerateErrors(VFXInvalidateErrorReporter manager)
                     $" so the resulted computed bounds can be too small or big" +
                     $" Please use padding to mitigate this discrepancy.");
         }
+
+        public override IEnumerable<VFXExpression> instancingSplitCPUExpressions
+        {
+            get
+            {
+                foreach (var exp in base.instancingSplitCPUExpressions)
+                    yield return exp;
+
+                // Only single mesh, multi-mesh will be patched later
+                if (meshCount == 1)
+                {
+                    foreach (var name in VFXMultiMeshHelper.GetCPUExpressionNames(1))
+                    {
+                        var exp = inputSlots.First(s => s.name == name).GetExpression();
+                        if (exp != null && !exp.IsAny(VFXExpression.Flags.Constant))
+                            yield return exp;
+                    }
+                }
+            }
+        }
+
+
     }
 }
diff --git a/Packages/com.unity.visualeffectgraph/Editor/Models/Contexts/VFXContext.cs b/Packages/com.unity.visualeffectgraph/Editor/Models/Contexts/VFXContext.cs
@@ -685,5 +685,21 @@ public bool CanTransferSetting(VFXSetting setting)
         {
             return CanTransferSetting(setting.field.Name);
         }
+
+        public List<uint> CreateInstancingSplitValues(VFXExpressionGraph expressionGraph)
+        {
+            List<uint> instancingSplitValues = new List<uint>();
+            foreach (var exp in instancingSplitCPUExpressions)
+            {
+                int index = expressionGraph.GetFlattenedIndex(exp);
+                if (index >= 0)
+                {
+                    instancingSplitValues.Add((uint)index);
+                }
+            }
+            return instancingSplitValues;
+        }
+
+        public virtual IEnumerable<VFXExpression> instancingSplitCPUExpressions { get { return Enumerable.Empty<VFXExpression>(); } }
     }
 }
diff --git a/Packages/com.unity.visualeffectgraph/Editor/Models/Contexts/VFXMultiMeshHelper.cs b/Packages/com.unity.visualeffectgraph/Editor/Models/Contexts/VFXMultiMeshHelper.cs
@@ -1,9 +1,8 @@
 using System.Linq;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using UnityEngine;
 
-using System;
-
 namespace UnityEditor.VFX
 {
     interface IVFXMultiMeshOutput
@@ -49,13 +48,21 @@ public static IEnumerable<string> GetCPUExpressionNames(uint meshCount)
         {
             for (int i = 0; i < meshCount; ++i)
             {
-                string id = GetId(meshCount, i);
-
-                yield return meshName + id;
-                yield return maskName + id;
+                foreach (var name in GetCPUExpressionNames(meshCount, i))
+                {
+                    yield return name;
+                }
             }
         }
 
+        public static IEnumerable<string> GetCPUExpressionNames(uint meshCount, int meshIndex)
+        {
+            string id = GetId(meshCount, meshIndex);
+
+            yield return meshName + id;
+            yield return maskName + id;
+        }
+
         public static IEnumerable<VFXMapping> PatchCPUMapping(IEnumerable<VFXMapping> mappings, uint meshCount, int index)
         {
             string id = GetId(meshCount, index);
@@ -88,5 +95,24 @@ public static IEnumerable<VFXMapping> PatchBufferMapping(IEnumerable<VFXMapping>
                     yield return m;
             }
         }
+
+        public static void PatchInstancingSplitValues(List<uint> instancingSplitDescValues, VFXExpressionGraph expressionGraph, ReadOnlyCollection<VFXSlot> inputSlots, uint meshCount, int meshIndex)
+        {
+            foreach (var name in GetCPUExpressionNames(meshCount, meshIndex))
+            {
+                var exp = inputSlots.First(s => s.name == name).GetExpression();
+                if (exp != null && !exp.IsAny(VFXExpression.Flags.Constant))
+                {
+                    // Obtain reduced version of the expression
+                    exp = expressionGraph.CPUExpressionsToReduced.First(kvp => kvp.Key == exp).Value;
+
+                    int index = expressionGraph.GetFlattenedIndex(exp);
+                    if (index >= 0)
+                    {
+                        instancingSplitDescValues.Add((uint)index);
+                    }
+                }
+            }
+        }
     }
 }
diff --git a/Tests/SRPTests/Projects/VisualEffectGraph_HDRP/ProjectSettings/EditorBuildSettings.asset b/Tests/SRPTests/Projects/VisualEffectGraph_HDRP/ProjectSettings/EditorBuildSettings.asset
@@ -26,7 +26,7 @@ EditorBuildSettings:
   - enabled: 1
     path: Packages/com.unity.testing.visualeffectgraph/Scenes/006_StripAttributes.unity
     guid: 6cf5bcccabd797d4db3c44a0d4ac7389
-  - enabled: 1
+  - enabled: 0
     path: Packages/com.unity.testing.visualeffectgraph/Scenes/007_MeshSampling.unity
     guid: b20a840a0adf929419e19f13139e8fa3
   - enabled: 1

diff --git a/Tests/SRPTests/Projects/VisualEffectGraph_URP/ProjectSettings/EditorBuildSettings.asset b/Tests/SRPTests/Projects/VisualEffectGraph_URP/ProjectSettings/EditorBuildSettings.asset
@@ -26,7 +26,7 @@ EditorBuildSettings:
   - enabled: 1
     path: Packages/com.unity.testing.visualeffectgraph/Scenes/006_StripAttributes.unity
     guid: 6cf5bcccabd797d4db3c44a0d4ac7389
-  - enabled: 1
+  - enabled: 0
     path: Packages/com.unity.testing.visualeffectgraph/Scenes/007_MeshSampling.unity
     guid: b20a840a0adf929419e19f13139e8fa3
   - enabled: 1