Custom Interpolator Feature (#3281)

* Initial merge for custom interpolator feature for Shader Graph.
* Changes made to HDRP and URP shaders, targets, and templates to support injecting additional interpolators.
* Rudimentary warning system for potential overuse.
SG:
* Generator modified to inject custom interpolators.
* Custom Interpolator Node added with searcher support.
* Packing modified to avoid unexpected conflicts and to support packing float1.
* Various other ShaderGraph systems modified to support the feature.

com.unity.render-pipelines.high-definition/Editor/Material/Decal/ShaderGraph/DecalSubTarget.cs

@@ -254,6 +254,7 @@ public static class DecalPasses
                 pragmas = DecalPragmas.Instanced,
                 defines = CoreDefines.ScenePicking,
                 includes = DecalIncludes.ScenePicking,
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             public static PassDescriptor DBufferProjector = new PassDescriptor()
@@ -274,6 +275,7 @@ public static class DecalPasses
                 pragmas = DecalPragmas.Instanced,
                 keywords = DecalDefines.Decals,
                 includes = DecalIncludes.Default,
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             public static PassDescriptor DecalProjectorForwardEmissive = new PassDescriptor()
@@ -296,6 +298,7 @@ public static class DecalPasses
                 pragmas = DecalPragmas.Instanced,
                 defines = DecalDefines.Emission,
                 includes = DecalIncludes.Default,
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             public static PassDescriptor DBufferMesh = new PassDescriptor()
@@ -319,6 +322,7 @@ public static class DecalPasses
                 pragmas = DecalPragmas.Instanced,
                 keywords = DecalDefines.Decals,
                 includes = DecalIncludes.Default,
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             public static PassDescriptor DecalMeshForwardEmissive = new PassDescriptor()
@@ -342,6 +346,7 @@ public static class DecalPasses
                 pragmas = DecalPragmas.Instanced,
                 defines = DecalDefines.Emission,
                 includes = DecalIncludes.Default,
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             public static PassDescriptor Preview = new PassDescriptor()
@@ -364,6 +369,7 @@ public static class DecalPasses
                 renderStates = DecalRenderStates.Preview,
                 pragmas = DecalPragmas.Instanced,
                 includes = DecalIncludes.Default,
+                customInterpolators = CoreCustomInterpolators.Common,
             };
         }
         #endregion

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/HDShaderPasses.cs

@@ -27,6 +27,7 @@ public static PassDescriptor GenerateDistortionPass(bool supportLighting)
                 pragmas = CorePragmas.DotsInstancedInV1AndV2,
                 defines = CoreDefines.ShaderGraphRaytracingDefault,
                 includes = GenerateIncludes(),
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             RenderStateCollection GenerateRenderState()
@@ -90,6 +91,7 @@ public static PassDescriptor GenerateScenePicking()
                 pragmas = CorePragmas.DotsInstancedInV1AndV2EditorSync,
                 defines = CoreDefines.ScenePicking,
                 includes = GenerateIncludes(),
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             IncludeCollection GenerateIncludes()
@@ -126,6 +128,7 @@ public static PassDescriptor GenerateSceneSelection(bool supportLighting)
                 pragmas = CorePragmas.DotsInstancedInV1AndV2EditorSync,
                 defines = CoreDefines.SceneSelection,
                 includes = GenerateIncludes(),
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             IncludeCollection GenerateIncludes()
@@ -176,6 +179,7 @@ static public PassDescriptor GenerateShadowCaster(bool supportLighting)
                 renderStates = CoreRenderStates.ShadowCaster,
                 pragmas = CorePragmas.DotsInstancedInV2Only,
                 includes = GenerateIncludes(),
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             IncludeCollection GenerateIncludes()
@@ -265,6 +269,7 @@ public static PassDescriptor GenerateDepthForwardOnlyPass(bool supportLighting)
                 pragmas = CorePragmas.DotsInstancedInV2Only,
                 defines = supportLighting ? CoreDefines.DepthForwardOnly : CoreDefines.DepthForwardOnlyUnlit,
                 includes = GenerateIncludes(),
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             RenderStateCollection GenerateRenderState()
@@ -331,6 +336,7 @@ public static PassDescriptor GenerateMotionVectors(bool supportLighting, bool su
                 defines = GenerateDefines(),
                 pragmas = CorePragmas.DotsInstancedInV2Only,
                 includes = GenerateIncludes(),
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             DefineCollection GenerateDefines()
@@ -402,6 +408,7 @@ public static PassDescriptor GenerateForwardOnlyPass(bool supportLighting)
                 includes = GenerateIncludes(),
 
                 virtualTextureFeedback = true,
+                customInterpolators = CoreCustomInterpolators.Common
             };
 
             FieldCollection GenerateRequiredFields()
@@ -509,6 +516,7 @@ public static PassDescriptor GenerateBackThenFront(bool supportLighting)
                 pragmas = CorePragmas.DotsInstancedInV1AndV2,
                 defines = CoreDefines.BackThenFront,
                 includes = GenerateIncludes(),
+                customInterpolators = CoreCustomInterpolators.Common
             };
 
             IncludeCollection GenerateIncludes()
@@ -583,6 +591,7 @@ public static PassDescriptor GenerateTransparentDepthPrepass(bool supportLightin
                 pragmas = CorePragmas.DotsInstancedInV1AndV2,
                 defines = CoreDefines.TransparentDepthPrepass,
                 includes = GenerateIncludes(),
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             RenderStateCollection GenerateRenderState()
@@ -669,6 +678,7 @@ public static PassDescriptor GenerateTransparentDepthPostpass(bool supportLighti
                 pragmas = CorePragmas.DotsInstancedInV1AndV2,
                 defines = CoreDefines.TransparentDepthPostpass,
                 includes = GenerateIncludes(),
+                customInterpolators = CoreCustomInterpolators.Common,
             };
 
             IncludeCollection GenerateIncludes()
@@ -725,6 +735,7 @@ public static PassDescriptor GenerateLitDepthOnly()
                 defines = CoreDefines.ShaderGraphRaytracingDefault,
                 keywords = LitDepthOnlyKeywords,
                 includes = DepthOnlyIncludes,
+                customInterpolators = CoreCustomInterpolators.Common,
             };
         }
 
@@ -766,7 +777,7 @@ public static PassDescriptor GenerateGBuffer()
                 defines = CoreDefines.ShaderGraphRaytracingDefault,
                 keywords = GBufferKeywords,
                 includes = GBufferIncludes,
-
+                customInterpolators = CoreCustomInterpolators.Common,
                 virtualTextureFeedback = true,
             };
         }
@@ -821,7 +832,7 @@ public static PassDescriptor GenerateLitForward()
                 pragmas = CorePragmas.DotsInstancedInV1AndV2,
                 defines = CoreDefines.Forward,
                 includes = ForwardIncludes,
-
+                customInterpolators = CoreCustomInterpolators.Common,
                 virtualTextureFeedback = true,
             };
         }

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/HDStructs.cs

@@ -29,6 +29,7 @@ static class HDStructs
         {
             name = "VaryingsMeshToPS",
             packFields = true,
+            populateWithCustomInterpolators = true,
             fields = new FieldDescriptor[]
             {
                 HDStructFields.VaryingsMeshToPS.positionCS,

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/HDTarget.cs

@@ -67,6 +67,9 @@ sealed class HDTarget : Target, IHasMetadata, ILegacyTarget
         [SerializeField]
         string m_CustomEditorGUI;
 
+        internal override bool ignoreCustomInterpolators => false;
+        internal override int padCustomInterpolatorLimit => 8;
+
         public override bool IsNodeAllowedByTarget(Type nodeType)
         {
             SRPFilterAttribute srpFilter = NodeClassCache.GetAttributeOnNodeType<SRPFilterAttribute>(nodeType);
@@ -1404,4 +1407,19 @@ static class CoreKeywordDescriptors
         };
     }
     #endregion
+
+    #region CustomInterpolators
+    static class CoreCustomInterpolators
+    {
+        public static readonly CustomInterpSubGen.Collection Common = new CustomInterpSubGen.Collection
+        {
+            CustomInterpSubGen.Descriptor.MakeDefine(CustomInterpSubGen.Splice.k_splicePreVertex, "USE_CUSTOMINTERP_APPLYMESHMOD"),
+            CustomInterpSubGen.Descriptor.MakeStruct(CustomInterpSubGen.Splice.k_splicePreInclude, "CustomInterpolators", "USE_CUSTOMINTERP_SUBSTRUCT"),
+            CustomInterpSubGen.Descriptor.MakeBlock("CustomInterpolatorVertexDefinitionToVaryings", "varyings", "vertexDescription"),
+            CustomInterpSubGen.Descriptor.MakeBlock("CustomInterpolatorVaryingsToFragInputs", "output.customInterpolators", "input"),
+            CustomInterpSubGen.Descriptor.MakeBlock(CustomInterpSubGen.Splice.k_spliceCopyToSDI, "output", "input.customInterpolators")
+        };
+    }
+
+    #endregion
 }

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/Templates/ShaderPass.template

@@ -24,6 +24,10 @@ Pass
     $splice(PassKeywords)
     $splice(GraphKeywords)
 
+    // For custom interpolators to inject a substruct definition before FragInputs definition,
+    // allowing for FragInputs to capture CI's intended for ShaderGraph's SDI.
+    $splice(CustomInterpolatorPreInclude)
+
     #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
     #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Texture.hlsl"
     #include "Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl"

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/Templates/SharedCode.template.hlsl

@@ -17,6 +17,9 @@ FragInputs BuildFragInputs(VaryingsMeshToPS input)
     $FragInputs.texCoord3:          output.texCoord3 = input.texCoord3;
     $FragInputs.color:              output.color = input.color;
 
+    // splice point to copy custom interpolator fields from varyings to frag inputs
+    $splice(CustomInterpolatorVaryingsToFragInputs)
+
     return output;
 }
 
@@ -60,6 +63,9 @@ SurfaceDescriptionInputs FragInputsToSurfaceDescriptionInputs(FragInputs input,
     $SurfaceDescriptionInputs.FaceSign:                  output.FaceSign =                    input.isFrontFace;
     $SurfaceDescriptionInputs.TimeParameters:            output.TimeParameters =              _TimeParameters.xyz; // This is mainly for LW as HD overwrite this value
 
+    // splice point to copy frag inputs custom interpolator pack into the SDI
+    $splice(CustomInterpolatorCopyToSDI)
+
     return output;
 }
 

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/Templates/VertexAnimation.template.hlsl

@@ -39,7 +39,17 @@ VertexDescriptionInputs AttributesMeshToVertexDescriptionInputs(AttributesMesh i
     return output;
 }
 
-AttributesMesh ApplyMeshModification(AttributesMesh input, float3 timeParameters)
+// This is used for injecting the define below.
+$splice(CustomInterpolatorPreVertex)
+
+
+
+    AttributesMesh ApplyMeshModification(AttributesMesh input, float3 timeParameters
+#if defined(USE_CUSTOMINTERP_APPLYMESHMOD) // mirrored in VertMesh.hlsl and MotionVectorVertexShaderCommon.hlsl
+        // use ifdef via TESSELLATION_ON to use VaryingsMeshToDS (Domain varyings instead of pixel varyings) whenever SG is modified to support Tess.
+        , inout VaryingsMeshToPS varyings
+#endif
+    )
 {
     // build graph inputs
     VertexDescriptionInputs vertexDescriptionInputs = AttributesMeshToVertexDescriptionInputs(input);
@@ -54,5 +64,8 @@ AttributesMesh ApplyMeshModification(AttributesMesh input, float3 timeParameters
     $VertexDescription.Normal:   input.normalOS = vertexDescription.Normal;
     $VertexDescription.Tangent:  input.tangentOS.xyz = vertexDescription.Tangent;
 
+    // The purpose of the above ifdef, this allows shader graph custom interpolators to write directly to the varyings structs.
+    $splice(CustomInterpolatorVertexDefinitionToVaryings)
+
     return input;
 }

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/ShaderPass/FragInputs.hlsl

@@ -30,6 +30,11 @@ struct FragInputs
 
     // For two sided lighting
     bool isFrontFace;
+
+    // append a substruct for custom interpolators to be copied correctly into SDI from Varyings.
+    #if defined(USE_CUSTOMINTERP_SUBSTRUCT)
+        CustomInterpolators customInterpolators;
+    #endif
 };
 
 void GetVaryingsDataDebug(uint paramId, FragInputs input, inout float3 result, inout bool needLinearToSRGB)

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/ShaderPass/MotionVectorVertexShaderCommon.hlsl

@@ -115,9 +115,14 @@ PackedVaryingsType MotionVectorVS(inout VaryingsType varyingsType, AttributesMes
     // Need to apply any vertex animation to the previous worldspace position, if we want it to show up in the motion vector buffer
 #if defined(HAVE_MESH_MODIFICATION)
         AttributesMesh previousMesh = inputMesh;
-        previousMesh.positionOS = effectivePositionOS ;
+        previousMesh.positionOS = effectivePositionOS;
+
+        previousMesh = ApplyMeshModification(previousMesh, _LastTimeParameters.xyz
+    #if defined(USE_CUSTOMINTERP_APPLYMESHMOD)
+            , varyingsType.vmesh
+    #endif
+            );
 
-        previousMesh = ApplyMeshModification(previousMesh, _LastTimeParameters.xyz);
         float3 previousPositionRWS = TransformPreviousObjectToWorld(previousMesh.positionOS);
 #else
         float3 previousPositionRWS = TransformPreviousObjectToWorld(effectivePositionOS);

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/ShaderPass/VertMesh.hlsl

@@ -131,12 +131,19 @@ VaryingsToDS InterpolateWithBaryCoordsToDS(VaryingsToDS input0, VaryingsToDS inp
 VaryingsMeshType VertMesh(AttributesMesh input, float3 worldSpaceOffset)
 {
     VaryingsMeshType output;
+    ZERO_INITIALIZE(VaryingsMeshType, output);
 
     UNITY_SETUP_INSTANCE_ID(input);
     UNITY_TRANSFER_INSTANCE_ID(input, output);
 
+
 #if defined(HAVE_MESH_MODIFICATION)
-    input = ApplyMeshModification(input, _TimeParameters.xyz);
+    input = ApplyMeshModification(input, _TimeParameters.xyz
+    // If custom interpolators are in use, we need to write them to the shader graph generated VaryingsMesh
+    #if defined(USE_CUSTOMINTERP_APPLYMESHMOD)
+        , output
+    #endif
+    );
 #endif
 
     // This return the camera relative position (if enable)

com.unity.render-pipelines.universal/Editor/ShaderGraph/Includes/Varyings.hlsl

@@ -19,6 +19,10 @@ Varyings BuildVaryings(Attributes input)
     VertexDescriptionInputs vertexDescriptionInputs = BuildVertexDescriptionInputs(input);
     VertexDescription vertexDescription = VertexDescriptionFunction(vertexDescriptionInputs);
 
+    #if defined(CUSTOMINTERPOLATOR_VARYPASSTHROUGH_FUNC)
+        CustomInterpolatorPassThroughFunc(output, vertexDescription);
+    #endif
+
     // Assign modified vertex attributes
     input.positionOS = vertexDescription.Position;
     #if defined(VARYINGS_NEED_NORMAL_WS)

com.unity.render-pipelines.universal/Editor/ShaderGraph/Targets/UniversalLitSubTarget.cs

@@ -386,6 +386,9 @@ static class LitPasses
                 pragmas  = CorePragmas.Forward,     // NOTE: SM 2.0 only GL
                 keywords = LitKeywords.Forward,
                 includes = LitIncludes.Forward,
+
+                // Custom Interpolator Support
+                customInterpolators = CoreCustomInterpDescriptors.Common
             };
 
             public static PassDescriptor ForwardOnly = new PassDescriptor
@@ -414,6 +417,9 @@ static class LitPasses
                 pragmas  = CorePragmas.Forward,    // NOTE: SM 2.0 only GL
                 keywords = LitKeywords.Forward,
                 includes = LitIncludes.Forward,
+
+                // Custom Interpolator Support
+                customInterpolators = CoreCustomInterpDescriptors.Common
             };
 
             // Deferred only in SM4.5, MRT not supported in GLES2
@@ -442,6 +448,9 @@ static class LitPasses
                 pragmas = CorePragmas.DOTSGBuffer,
                 keywords = LitKeywords.GBuffer,
                 includes = LitIncludes.GBuffer,
+
+                // Custom Interpolator Support
+                customInterpolators = CoreCustomInterpDescriptors.Common
             };
 
             public static PassDescriptor Meta = new PassDescriptor()
@@ -469,6 +478,9 @@ static class LitPasses
                 pragmas = CorePragmas.Default,
                 keywords = LitKeywords.Meta,
                 includes = LitIncludes.Meta,
+
+                // Custom Interpolator Support
+                customInterpolators = CoreCustomInterpDescriptors.Common
             };
 
             public static readonly PassDescriptor _2D = new PassDescriptor()
@@ -493,6 +505,9 @@ static class LitPasses
                 renderStates = CoreRenderStates.Default,
                 pragmas = CorePragmas.Instanced,
                 includes = LitIncludes._2D,
+
+                // Custom Interpolator Support
+                customInterpolators = CoreCustomInterpDescriptors.Common
             };
 
             public static readonly PassDescriptor DepthNormalOnly = new PassDescriptor()
@@ -520,6 +535,9 @@ static class LitPasses
                 renderStates = CoreRenderStates.DepthNormalsOnly,
                 pragmas = CorePragmas.Instanced,
                 includes = CoreIncludes.DepthNormalsOnly,
+
+                // Custom Interpolator Support
+                customInterpolators = CoreCustomInterpDescriptors.Common
             };
         }
         #endregion