HDRenderPipeline: Attempt to do somerthing with velocity pass

Assets/ScriptableRenderLoop/HDRenderPipeline/Material/Lit/LitAttributesVarying.hlsl

 #ifdef ATTRIBUTES_WANT_COLOR
     float4 color        : COLOR;
 #endif
+
+#ifdef VARYING_WANT_PASS_SPECIFIC
+    AttributesPass attributesPass;
+#endif
+
     // UNITY_INSTANCE_ID
 };
 
 #endif
 #ifdef VARYING_WANT_COLOR   
     float4 color;
+#endif
+#ifdef VARYING_WANT_PASS_SPECIFIC
+    VaryingsPass varyingPass;
 #endif
 };
 
 
     // Allocate only necessary space if shader compiler in the future are able to automatically pack
 #ifdef VARYING_WANT_TEXCOORD1
-    float4 interpolators4 : TEXCOORD3;
+    float4 interpolators4 : TEXCOORD4;
-    float2 interpolators4 : TEXCOORD3;
+    float2 interpolators4 : TEXCOORD4;
-    float4 interpolators5 : TEXCOORD4;
+    float4 interpolators5 : TEXCOORD5;
-    float2 interpolators5 : TEXCOORD4;
+    float2 interpolators5 : TEXCOORD5;
+#endif
+
+#ifdef VARYING_WANT_PASS_SPECIFIC
+    PackedVaryingsPass packedVaryingsPass;
 #endif
 
 #if defined(VARYING_WANT_CULLFACE) && SHADER_STAGE_FRAGMENT
     output.interpolators6 = input.color;
 #endif
 
+#ifdef VARYING_WANT_PASS_SPECIFIC
+    output.packedVaryingsPass = PackVaryingsPass(input.varyingPass);
+#endif
+
     return output;
 }
 
     output.color = input.interpolators6;
 #endif
 
+#ifdef VARYING_WANT_PASS_SPECIFIC
+    output.varyingPass = UnpackVaryingsPass(input.packedVaryingsPass);
+#endif
+
 #if defined(VARYING_WANT_CULLFACE) && SHADER_STAGE_FRAGMENT
     output.isFrontFace = IS_FRONT_VFACE(input.cullFace, true, false);
 #endif
 #if defined(VARYING_WANT_COLOR) || defined(ATTRIBUTES_WANT_COLOR)
 float4 VARYING_DS_WANT_COLOR;
 #endif
-
-#endif // TESSELLATION_ON
 
 // Varying for domain shader
 // Position and normal are always present (for tessellation) and in world space

Assets/ScriptableRenderLoop/HDRenderPipeline/Material/Lit/ShaderPass/LitVelocityPass.hlsl

 
 // TODO: For now disable per pixel and per vertex displacement mapping with motion vector
 // as vertex normal is not available + force UV0 for alpha test (not compatible with layered system...)
+#define VARYING_WANT_POSITION_WS
+#define VARYING_WANT_PASS_SPECIFIC
-struct Attributes
+#if defined(_ALPHATEST_ON)
+#define ATTRIBUTES_WANT_UV0
+    #ifdef LAYERED_LIT_SHADER
+    #define ATTRIBUTES_WANT_UV1
+        #if defined(_REQUIRE_UV2) || defined(_REQUIRE_UV3)
+        #define ATTRIBUTES_WANT_UV2
+        #endif
+        #if defined(_REQUIRE_UV3)
+        #define ATTRIBUTES_WANT_UV3
+        #endif
+    #endif
+#endif
+
+#if defined(_ALPHATEST_ON)
+#define VARYING_WANT_TEXCOORD0
+    #ifdef LAYERED_LIT_SHADER
+    #define VARYING_WANT_TEXCOORD1
+        #if defined(_REQUIRE_UV2) || defined(_REQUIRE_UV3)
+        #define VARYING_WANT_TEXCOORD2
+        #endif
+        #if defined(_REQUIRE_UV3)
+        #define VARYING_WANT_TEXCOORD3
+        #endif
+    #endif
+#endif
+
+// Available semantic start from TEXCOORD4
+struct AttributesPass
-    float3 positionOS : POSITION;
-    float2 uv0 : TEXCOORD0;
-struct Varyings
+struct VaryingsPass
-    float4 positionCS;
-    float3 positionWS;
-    float2 texCoord0;
-struct PackedVaryings
+// Available interpolator start from TEXCOORD8
+struct PackedVaryingsPass
-    float4 positionCS : SV_Position;
-#if NEED_TANGENT_TO_WORLD
-    float4 interpolators[5] : TEXCOORD0;
-#elif NEED_TEXCOORD0
-    float4 interpolators[3] : TEXCOORD0;
-#else
-    float4 interpolators[3] : TEXCOORD0;
-#endif
+    // Note: Z component is not use
+    float3 interpolators0 : TEXCOORD8
+    float3 interpolators1 : TEXCOORD9;
-// Function to pack data to use as few interpolator as possible, the ShaderGraph should generate these functions
-PackedVaryings PackVaryings(Varyings input)
+PackedVaryingsPass PackVaryingsPass(VaryingsPass input)
-    PackedVaryings output;
-    output.positionCS = input.positionCS;
-    output.interpolators[0] = float4(input.positionWS, 0.0);
-    output.interpolators[1] = float4(input.transferPositionCS.xyw, 0.0);
-    output.interpolators[2] = float4(input.transferPreviousPositionCS.xyw, 0.0);
+    PackedVaryingsPass output;
+    output.interpolators0 = float3(input.transferPositionCS.xyw);
+    output.interpolators1 = float3(input.transferPreviousPositionCS.xyw);
+}
-#if NEED_TANGENT_TO_WORLD
-    output.interpolators[0].w = input.texCoord0.x;
-    output.interpolators[1].w = input.texCoord0.y;
-
-    output.interpolators[3].xyz = input.tangentToWorld[0];
-    output.interpolators[4].xyz = input.tangentToWorld[1];
+VaryingsPass UnpackVaryingsPass(PackedVaryingsPass input)
+{
+    PackedVaryingsPass output;
+    output.interpolators0 = float3(input.transferPositionCS.xyw);
+    output.interpolators1 = float3(input.transferPreviousPositionCS.xyw);
+}
-    output.interpolators[2].w = input.tangentToWorld[2].x;
-    output.interpolators[3].w = input.tangentToWorld[2].y;
-    output.interpolators[4].w = input.tangentToWorld[2].z;
-#elif NEED_TEXCOORD0
-    output.interpolators[0].w = input.texCoord0.x;
-    output.interpolators[1].w = input.texCoord0.y;
-#endif
-
-    return output;
-}
 
 FragInputs UnpackVaryings(PackedVaryings input)
 {

Assets/ScriptableRenderLoop/HDRenderPipeline/ShaderPass/ShaderPassVelocity.hlsl

 #error SHADERPASS_is_not_correctly_define
 #endif
 
+#if SHADER_STAGE_VERTEX
+
+#endif
+
+#if SHADER_STAGE_FRAGMENT
+
 float4 Frag(PackedVaryings packedInput) : SV_Target
 {
     FragInputs input = UnpackVaryings(packedInput);
     return outBuffer;
 }
 
+#endif
+
+
+