[VFX][Fix] Fix Screen Space Size (and other) block in ShaderGraph outputs

This PR fixes the blocks that are implicitly using TransformObjectToWorld (e.g. Screen Space Size) in a ShaderGraph output.
Prior to this PR, the block was trying to use `UNITY_MATRIX_M `which is redefined as `elementToWorld` ("particle -> world matrix), instead of the "object -> world" matrix. It now uses the correct matrix.
Additionally, the selection & picking passes were broken when using blocks like Screen Space Size so it required change.

Author: ludovic-theobald

Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/PickingSpaceTransforms.hlsl

@@ -115,7 +115,11 @@ float4x4 ScenePickingGetCameraViewProjMatrix()
 #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/SpaceTransforms.hlsl"
 
 #if defined(HAVE_VFX_MODIFICATION)
-#define VFX_APPLY_CAMERA_POSITION_IN_ELEMENT_MATRIX 1
+#define VFX_HAS_PICKING_MATRIX_CORRECTION 1
+#define GetSGVFXUnityObjectToWorld     GetSGVFXUnityObjectToWorld_Picking
+#define GetSGVFXUnityWorldToObject     GetSGVFXUnityWorldToObject_Picking
+float4x4 GetSGVFXUnityObjectToWorld()     { return RevertCameraTranslationFromMatrix(GetSGVFXUnityObjectToWorldBackup()); }
+float4x4 GetSGVFXUnityWorldToObject()     { return RevertCameraTranslationFromInverseMatrix(GetSGVFXUnityWorldToObjectBackup()); }
 #endif
 
 #endif

Packages/com.unity.render-pipelines.high-definition/Runtime/VFXGraph/Shaders/VFXCommon.hlsl

@@ -54,6 +54,46 @@ float2 VFXGetNormalizedScreenSpaceUV(float4 clipPos)
     return clipPos.xy * frac(_ScreenParams.zw);
 }
 
+float4x4 VFXGetObjectToWorldMatrix()
+{
+    #if defined(SHADER_STAGE_RAY_TRACING)
+    float3x4 objToWorld3x4 = ObjectToWorld3x4();
+    float4x4 objToWorld = float4x4(
+        objToWorld3x4._m00, objToWorld3x4._m01, objToWorld3x4._m02, objToWorld3x4._m03,
+        objToWorld3x4._m10, objToWorld3x4._m11, objToWorld3x4._m12, objToWorld3x4._m13,
+        objToWorld3x4._m20, objToWorld3x4._m21, objToWorld3x4._m22, objToWorld3x4._m23,
+        0,0,0,1);
+    return objToWorld;
+    #else
+    // NOTE: If using the new generation path, explicitly call the object matrix (since the particle matrix is now baked into UNITY_MATRIX_M)
+    #if defined(HAVE_VFX_MODIFICATION) && !defined(SHADER_STAGE_COMPUTE)
+    return GetSGVFXUnityObjectToWorld();
+    #else
+    return GetObjectToWorldMatrix();
+    #endif
+    #endif
+}
+
+float4x4 VFXGetWorldToObjectMatrix()
+{
+    #if defined(SHADER_STAGE_RAY_TRACING)
+    float3x4 worldToObj3x4 = WorldToObject3x4();
+    float4x4 worldToObj = float4x4(
+        worldToObj3x4._m00, worldToObj3x4._m01, worldToObj3x4._m02, worldToObj3x4._m03,
+        worldToObj3x4._m10, worldToObj3x4._m11, worldToObj3x4._m12, worldToObj3x4._m13,
+        worldToObj3x4._m20, worldToObj3x4._m21, worldToObj3x4._m22, worldToObj3x4._m23,
+        0,0,0,1);
+    return worldToObj;
+    #else
+    // NOTE: If using the new generation path, explicitly call the object matrix (since the particle matrix is now baked into UNITY_MATRIX_I_M)
+    #if defined(HAVE_VFX_MODIFICATION) && !defined(SHADER_STAGE_COMPUTE)
+    return GetSGVFXUnityWorldToObject();
+    #else
+    return GetWorldToObjectMatrix();
+    #endif
+    #endif
+}
+
 float4 VFXTransformPositionWorldToClip(float3 posWS)
 {
 #if VFX_WORLD_SPACE
@@ -64,7 +104,7 @@ float4 VFXTransformPositionWorldToClip(float3 posWS)
 
 float4 VFXTransformPositionObjectToNonJitteredClip(float3 posOS)
 {
-    float3 posWS = TransformObjectToWorld(posOS);
+    float3 posWS = mul(VFXGetObjectToWorldMatrix(), float4(posOS,1)).xyz;
     return mul(UNITY_MATRIX_UNJITTERED_VP, float4(posWS, 1.0f));
 }
 
@@ -81,7 +121,7 @@ float3 VFXTransformPreviousObjectToWorld(float3 posOS)
 
 float4 VFXTransformPositionObjectToClip(float3 posOS)
 {
-    float3 posWS = TransformObjectToWorld(posOS);
+    float3 posWS = mul(VFXGetObjectToWorldMatrix(), float4(posOS,1)).xyz;
     return VFXTransformPositionWorldToClip(posWS);
 }
 
@@ -102,46 +142,6 @@ float3 VFXTransformPositionWorldToCameraRelative(float3 posWS)
 #endif
 }
 
-float4x4 VFXGetObjectToWorldMatrix()
-{
-#if defined(SHADER_STAGE_RAY_TRACING)
-    float3x4 objToWorld3x4 = ObjectToWorld3x4();
-    float4x4 objToWorld = float4x4(
-        objToWorld3x4._m00, objToWorld3x4._m01, objToWorld3x4._m02, objToWorld3x4._m03,
-        objToWorld3x4._m10, objToWorld3x4._m11, objToWorld3x4._m12, objToWorld3x4._m13,
-        objToWorld3x4._m20, objToWorld3x4._m21, objToWorld3x4._m22, objToWorld3x4._m23,
-        0,0,0,1);
-    return objToWorld;
-#else
-    // NOTE: If using the new generation path, explicitly call the object matrix (since the particle matrix is now baked into UNITY_MATRIX_M)
-#if defined(HAVE_VFX_MODIFICATION) && !defined(SHADER_STAGE_COMPUTE)
-    return GetSGVFXUnityObjectToWorld();
-    #else
-        return GetObjectToWorldMatrix();
-    #endif
-#endif
-}
-
-float4x4 VFXGetWorldToObjectMatrix()
-{
-#if defined(SHADER_STAGE_RAY_TRACING)
-    float3x4 worldToObj3x4 = WorldToObject3x4();
-    float4x4 worldToObj = float4x4(
-        worldToObj3x4._m00, worldToObj3x4._m01, worldToObj3x4._m02, worldToObj3x4._m03,
-        worldToObj3x4._m10, worldToObj3x4._m11, worldToObj3x4._m12, worldToObj3x4._m13,
-        worldToObj3x4._m20, worldToObj3x4._m21, worldToObj3x4._m22, worldToObj3x4._m23,
-        0,0,0,1);
-    return worldToObj;
-#else
-    // NOTE: If using the new generation path, explicitly call the object matrix (since the particle matrix is now baked into UNITY_MATRIX_I_M)
-#if defined(HAVE_VFX_MODIFICATION) && !defined(SHADER_STAGE_COMPUTE)
-    return GetSGVFXUnityWorldToObject();
-    #else
-        return GetWorldToObjectMatrix();
-    #endif
-#endif
-}
-
 float3x3 VFXGetWorldToViewRotMatrix()
 {
     return (float3x3)GetWorldToViewMatrix();

Packages/com.unity.render-pipelines.universal/Runtime/VFXGraph/Shaders/VFXCommon.hlsl

@@ -33,6 +33,26 @@ void VFXEncodeMotionVector(float2 velocity, out float4 outBuffer)
     outBuffer = float4(velocity.xy, 0, 0);
 }
 
+float4x4 VFXGetObjectToWorldMatrix()
+{
+    // NOTE: If using the new generation path, explicitly call the object matrix (since the particle matrix is now baked into UNITY_MATRIX_M)
+    #if defined(HAVE_VFX_MODIFICATION) && !defined(SHADER_STAGE_COMPUTE)
+    return GetSGVFXUnityObjectToWorld();
+    #else
+    return GetObjectToWorldMatrix();
+    #endif
+}
+
+float4x4 VFXGetWorldToObjectMatrix()
+{
+    // NOTE: If using the new generation path, explicitly call the object matrix (since the particle matrix is now baked into UNITY_MATRIX_I_M)
+    #if defined(HAVE_VFX_MODIFICATION) && !defined(SHADER_STAGE_COMPUTE)
+    return GetSGVFXUnityWorldToObject();
+    #else
+    return GetWorldToObjectMatrix();
+    #endif
+}
+
 float4 VFXTransformPositionWorldToClip(float3 posWS)
 {
     return TransformWorldToHClip(posWS);
@@ -50,13 +70,13 @@ float4 VFXTransformPositionWorldToPreviousClip(float3 posWS)
 
 float4 VFXTransformPositionObjectToClip(float3 posOS)
 {
-    float3 posWS = TransformObjectToWorld(posOS);
+    float3 posWS = mul(VFXGetObjectToWorldMatrix(), float4(posOS,1)).xyz;
     return VFXTransformPositionWorldToClip(posWS);
 }
 
 float4 VFXTransformPositionObjectToNonJitteredClip(float3 posOS)
 {
-    float3 posWS = TransformObjectToWorld(posOS);
+    float3 posWS = mul(VFXGetObjectToWorldMatrix(), float4(posOS,1)).xyz;
     return VFXTransformPositionWorldToNonJitteredClip(posWS);
 }
 
@@ -95,26 +115,6 @@ float4x4 ApplyCameraTranslationToInverseMatrix(float4x4 inverseModelMatrix)
 }
 //End of compatibility functions
 
-float4x4 VFXGetObjectToWorldMatrix()
-{
-    // NOTE: If using the new generation path, explicitly call the object matrix (since the particle matrix is now baked into UNITY_MATRIX_M)
-#if defined(HAVE_VFX_MODIFICATION) && !defined(SHADER_STAGE_COMPUTE)
-    return GetSGVFXUnityObjectToWorld();
-#else
-    return GetObjectToWorldMatrix();
-#endif
-}
-
-float4x4 VFXGetWorldToObjectMatrix()
-{
-    // NOTE: If using the new generation path, explicitly call the object matrix (since the particle matrix is now baked into UNITY_MATRIX_I_M)
-#if defined(HAVE_VFX_MODIFICATION) && !defined(SHADER_STAGE_COMPUTE)
-    return GetSGVFXUnityWorldToObject();
-#else
-    return GetWorldToObjectMatrix();
-#endif
-}
-
 float3x3 VFXGetWorldToViewRotMatrix()
 {
     return (float3x3)GetWorldToViewMatrix();

Packages/com.unity.visualeffectgraph/Editor/ShaderGraph/Templates/VFXConfig.template.hlsl

@@ -284,7 +284,7 @@ void SetupVFXMatrices(AttributesElement element, inout VFX_SRP_VARYINGS output)
 
 #if VFX_LOCAL_SPACE
     elementToWorld = mul(GetSGVFXUnityObjectToWorld(), elementToWorld);
-#else
+#elif !defined(VFX_HAS_PICKING_MATRIX_CORRECTION)
     elementToWorld = ApplyCameraTranslationToMatrix(elementToWorld);
 #endif
 
@@ -301,18 +301,10 @@ void SetupVFXMatrices(AttributesElement element, inout VFX_SRP_VARYINGS output)
 
 #if VFX_LOCAL_SPACE
     worldToElement = mul(worldToElement,GetSGVFXUnityWorldToObject());
-#else
+#elif !defined(VFX_HAS_PICKING_MATRIX_CORRECTION)
     worldToElement = ApplyCameraTranslationToInverseMatrix(worldToElement);
 #endif
 
-#if VFX_APPLY_CAMERA_POSITION_IN_ELEMENT_MATRIX
-    //Specific to PickingSpaceTransforms.hlsl (in HDRP so far)
-    //SHADEROPTIONS_CAMERA_RELATIVE_RENDERING has been undef at this stage
-    //Avoid removing twice _WorldSpaceCameraPos
-    elementToWorld = RevertCameraTranslationFromMatrix(elementToWorld);
-    worldToElement = RevertCameraTranslationFromInverseMatrix(worldToElement);
-#endif
-
     // Pack matrices into interpolator if requested by any node.
 #ifdef VARYINGS_NEED_ELEMENT_TO_WORLD
     output.elementToWorld0 = elementToWorld[0];

Packages/com.unity.visualeffectgraph/Shaders/VFXMatricesOverride.hlsl

@@ -30,8 +30,11 @@ static float4x4 vfxWorldToLocal;
 #else //SHADER_STAGE_COMPUTE
 
 //Store the previous definition of UNITY_MATRIX_M/I_M
-float4x4 GetSGVFXUnityObjectToWorld()     { return UNITY_MATRIX_M; }
-float4x4 GetSGVFXUnityWorldToObject()     { return UNITY_MATRIX_I_M; }
+float4x4 GetSGVFXUnityObjectToWorldBackup()     { return UNITY_MATRIX_M; }
+float4x4 GetSGVFXUnityWorldToObjectBackup()     { return UNITY_MATRIX_I_M; }
+
+float4x4 GetSGVFXUnityObjectToWorld()     { return GetSGVFXUnityObjectToWorldBackup(); }
+float4x4 GetSGVFXUnityWorldToObject()     { return GetSGVFXUnityWorldToObjectBackup(); }
 
 // Abstraction of Unity matrices for VFX element/particles.
 #undef  UNITY_MATRIX_M