Motion Vector Support

HDRenderpipeline changes to support Motion Vector Pass.

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Editor/BaseLitUI.cs

         static public void SetupBaseLitMaterialPass(Material material)
         {
             SetupBaseUnlitMaterialPass(material);
+
+            bool windEnabled = material.GetFloat(kWindEnabled) > 0.0f;
+            bool enableVertexDisplacement = (DisplacementMode)material.GetFloat(kDisplacementMode) == DisplacementMode.Vertex;
+            
+            material.SetShaderPassEnabled(HDShaderPassNames.s_MotionVectorsStr, windEnabled || enableVertexDisplacement);
+
         }
     }
 } // namespace UnityEditor

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitDataMeshModification.hlsl

     return ComputePerVertexDisplacement(layerTexCoord, vertexColor, lod) * normalWS;
 }
 
-void ApplyVertexModification(AttributesMesh input, float3 normalWS, inout float3 positionWS)
+void ApplyVertexModification(AttributesMesh input, float3 normalWS, inout float3 positionWS, float4 time)
 {
 #if defined(_VERTEX_DISPLACEMENT)
 
     
 #ifdef _VERTEX_WIND
     float3 rootWP = mul(GetObjectToWorldMatrix(), float4(0, 0, 0, 1)).xyz;
-    ApplyWindDisplacement(positionWS, normalWS, rootWP, _Stiffness, _Drag, _ShiverDrag, _ShiverDirectionality, _InitialBend, input.color.a, _Time);
+    ApplyWindDisplacement(positionWS, normalWS, rootWP, _Stiffness, _Drag, _ShiverDrag, _ShiverDirectionality, _InitialBend, input.color.a, time);
 #endif
 }
 

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/ShaderPass/LitVelocityPass.hlsl

 // conflict with the normal in the semantic. This need to be fix! Also no per pixel displacement is possible either.
 
 // Attributes
-#define REQUIRE_TANGENT_TO_WORLD 0 /* defined(_PIXEL_DISPLACEMENT) */
-#define REQUIRE_NORMAL 0 /*  defined(TESSELLATION_ON) || REQUIRE_TANGENT_TO_WORLD || defined(_VERTEX_WIND) || defined(_VERTEX_DISPLACEMENT) */
+#define REQUIRE_TANGENT_TO_WORLD defined(_PIXEL_DISPLACEMENT)
+#define REQUIRE_NORMAL defined(TESSELLATION_ON) || REQUIRE_TANGENT_TO_WORLD || defined(_VERTEX_WIND) || defined(_VERTEX_DISPLACEMENT)
 #define REQUIRE_VERTEX_COLOR ((defined(_VERTEX_DISPLACEMENT) || defined(_TESSELLATION_DISPLACEMENT)) && defined(LAYERED_LIT_SHADER) && (defined(_LAYER_MASK_VERTEX_COLOR_MUL) || defined(_LAYER_MASK_VERTEX_COLOR_ADD))) || defined(_VERTEX_WIND)
 
 // This first set of define allow to say which attributes will be use by the mesh in the vertex and domain shader (for tesselation)

ScriptableRenderPipeline/HDRenderPipeline/ShaderPass/ShaderPassVelocity.hlsl

 // Available semantic start from TEXCOORD4
 struct AttributesPass
 {
-    float3 previousPositionOS : NORMAL; // Contain previous transform position (in case of skinning for example)
+    float3 previousPositionOS : TEXCOORD4; // Contain previous transform position (in case of skinning for example)
 
     // TODO: Caution - For now the tesselation doesn't displace along the normal with Velocity shader as the previous previous position
     // conflict with the normal in the semantic. This need to be fix!
 #define VARYINGS_NEED_PASS
 #include "VertMesh.hlsl"
 
+void PositionZBias(VaryingsToPS input)
+{
+	#if defined(UNITY_REVERSED_Z)
+		input.vmesh.positionCS.z -= unity_MotionVectorsParams.z * input.vmesh.positionCS.w;
+	#else
+		input.vmesh.positionCS.z += unity_MotionVectorsParams.z * input.vmesh.positionCS.w;
+	#endif
+}
+
 PackedVaryingsType Vert(AttributesMesh inputMesh,
                         AttributesPass inputPass)
 {
+#if !defined(TESSELLATION_ON)
+	PositionZBias(varyingsType);
+#endif
+
-    varyingsType.vpass.positionCS = mul(_NonJitteredViewProjMatrix, mul(unity_ObjectToWorld, float4(inputMesh.positionOS, 1.0)));
-    varyingsType.vpass.previousPositionCS = mul(_PrevViewProjMatrix, mul(unity_MatrixPreviousM, unity_MotionVectorsParams.x ? float4(inputPass.previousPositionOS, 1.0) : float4(inputMesh.positionOS, 1.0)));
+	varyingsType.vpass.positionCS = mul(_NonJitteredViewProjMatrix, float4(varyingsType.vmesh.positionWS, 1.0));
+
+	//Need to apply any vertex animation to the previous worldspace position, if we want it to show up in the velocity buffer
+	float3 previousPositionWS = mul(unity_MatrixPreviousM, unity_MotionVectorsParams.x ? float4(inputPass.previousPositionOS, 1.0) : float4(inputMesh.positionOS, 1.0)).xyz;
+	#ifdef ATTRIBUTES_NEED_NORMAL
+		float3 normalWS = normalize(mul(inputMesh.normalOS, (float3x3)unity_MatrixPreviousMI));
+	#else
+		float3 normalWS = float3(0.0, 0.0, 0.0);
+	#endif
+		
+	#if defined(HAVE_VERTEX_MODIFICATION)
+		ApplyVertexModification(inputMesh, normalWS, previousPositionWS, _LastTime);
+	#endif
+	
+	//Need this since we are using the current position from VertMesh()
+	previousPositionWS = GetCameraRelativePositionWS(previousPositionWS);
+	
+	varyingsType.vpass.previousPositionCS = mul(_PrevViewProjMatrix, float4(previousPositionWS, 1.0));
 
     return PackVaryingsType(varyingsType);
 }
     VaryingsToPS output;
 
     output.vmesh = VertMeshTesselation(input.vmesh);
+
+	PositionZBias(output);
 
     output.vpass.positionCS = input.vpass.positionCS;
     output.vpass.previousPositionCS = input.vpass.previousPositionCS;

ScriptableRenderPipeline/HDRenderPipeline/ShaderPass/VertMesh.hlsl

 
     // TODO: deal with camera center rendering and instancing (This is the reason why we always perform two  steps transform to clip space + instancing matrix)
 
-    // This code is disabled for velocity pass for now because at the moment we cannot have Normals with the velocity pass (this attributes holds last frame data)
-    // TODO: Remove the velocity pass test when velocity is properly handled.
-#if defined(HAVE_VERTEX_MODIFICATION) && (SHADERPASS != SHADERPASS_VELOCITY)
-    ApplyVertexModification(input, normalWS, positionWS);
+#if defined(HAVE_VERTEX_MODIFICATION)
+    ApplyVertexModification(input, normalWS, positionWS, _Time);
 #endif
 
     positionWS = GetCameraRelativePositionWS(positionWS);
-    // TODO: TEMP: Velocity has a flow as it doens't have normal. This need to be fix. In the mean time, generate fix normal so compiler doesn't complain - When fix, think to also enable ATTRIBUTES_NEED_NORMAL in LitVelocityPass.hlsl
-    #if (SHADERPASS == SHADERPASS_VELOCITY)
-    output.normalWS = float3(0.0, 0.0, 1.0);
-    #else
-    #endif
     #if defined(VARYINGS_NEED_TANGENT_TO_WORLD) || defined(VARYINGS_DS_NEED_TANGENT)
     output.tangentWS = tangentWS;
     #endif

ScriptableRenderPipeline/HDRenderPipeline/ShaderVariables.hlsl

 CBUFFER_START(UnityPerCamera)
     // Time (t = time since current level load) values from Unity
     float4 _Time; // (t/20, t, t*2, t*3)
+    float4 _LastTime; // Last frame time (t/20, t, t*2, t*3)
     float4 _SinTime; // sin(t/8), sin(t/4), sin(t/2), sin(t)
     float4 _CosTime; // cos(t/8), cos(t/4), cos(t/2), cos(t)
     float4 unity_DeltaTime; // dt, 1/dt, smoothdt, 1/smoothdt
     float4x4 unity_MatrixNonJitteredVP;
     float4x4 unity_MatrixPreviousVP;
     float4x4 unity_MatrixPreviousM;
+	float4x4 unity_MatrixPreviousMI;
     float4 unity_MotionVectorsParams;
 CBUFFER_END