(wip) Use depth to discard pixels in front of distortion object

SampleScenes/HDTest/GraphicTest/Common/Material/Mat_Distorsion_Lit_Only_2DNoise.mat

     - _DistortionBlendMode: 0
     - _DistortionBlendOp: 0
     - _DistortionBlurBlendMode: 0
-    - _DistortionBlurDstBlend: 0
+    - _DistortionBlurDstBlend: 1
-    - _DistortionBlurSrcBlend: 0
+    - _DistortionBlurSrcBlend: 1
     - _DistortionDepthTest: 0
     - _DistortionDstBlend: 1
     - _DistortionEnable: 1

SampleScenes/HDTest/GraphicTest/Common/Material/Mat_Distorsion_Lit_Only_Ripple.mat

     - _DetailAlbedoScale: 1
     - _DetailNormalScale: 1
     - _DetailSmoothnessScale: 1
-    - _DistortionBlendMode: 1
+    - _DistortionBlendMode: 0
-    - _DistortionBlurDstBlend: 0
+    - _DistortionBlurDstBlend: 1
-    - _DistortionBlurSrcBlend: 8
+    - _DistortionBlurSrcBlend: 1
-    - _DistortionDstBlend: 0
+    - _DistortionDstBlend: 1
-    - _DistortionScale: 0
-    - _DistortionSrcBlend: 2
+    - _DistortionScale: 1
+    - _DistortionSrcBlend: 1
     - _DistortionStencilRef: 4
     - _DoubleSidedEnable: 0
     - _DoubleSidedNormalMode: 1

SampleScenes/HDTest/GraphicTest/Common/Material/Mat_Distorsion_Lit_Reject.mat

     - _DistortionBlurBlendMode: 0
     - _DistortionBlurDstBlend: 0
     - _DistortionBlurScale: 0
-    - _DistortionBlurSrcBlend: 0
+    - _DistortionBlurSrcBlend: 7
     - _DistortionDepthTest: 0
     - _DistortionDstBlend: 0
     - _DistortionEnable: 1

SampleScenes/HDTest/GraphicTest/Common/Material/Mat_Distorsion_Unlit_2DNoise.mat

     - _DetailAlbedoScale: 1
     - _DetailNormalScale: 1
     - _DetailSmoothnessScale: 1
+    - _DistortionBlendMode: 0
+    - _DistortionBlurBlendMode: 0
+    - _DistortionBlurDstBlend: 1
+    - _DistortionBlurScale: 1
+    - _DistortionBlurSrcBlend: 1
+    - _DistortionDstBlend: 1
+    - _DistortionScale: 1
+    - _DistortionSrcBlend: 1
     - _DistortionStencilRef: 4
     - _DoubleSidedEnable: 0
     - _DoubleSidedNormalMode: 1

SampleScenes/HDTest/GraphicTest/Common/Material/Mat_Distorsion_Unlit_Only_2DNoise.mat

   - DepthOnly
   - MOTIONVECTORS
   - Forward
+  - ForwardOnlyOpaqueDepthOnly
+  - ForwardOnlyOpaque
+  - GBufferWithPrepass
+  - TransparentDepthPrepass
   m_SavedProperties:
     serializedVersion: 3
     m_TexEnvs:
     - _DetailAlbedoScale: 1
     - _DetailNormalScale: 1
     - _DetailSmoothnessScale: 1
+    - _DistortionBlendMode: 0
+    - _DistortionBlurBlendMode: 0
+    - _DistortionBlurDstBlend: 1
+    - _DistortionBlurScale: 1
+    - _DistortionBlurSrcBlend: 1
+    - _DistortionDstBlend: 1
+    - _DistortionScale: 1
+    - _DistortionSrcBlend: 1
     - _DistortionStencilRef: 4
     - _DoubleSidedEnable: 0
     - _DoubleSidedNormalMode: 1

SampleScenes/HDTest/GraphicTest/Common/Material/Mat_Distorsion_Unlit_Only_Ripple.mat

   - DepthOnly
   - MOTIONVECTORS
   - Forward
+  - ForwardOnlyOpaqueDepthOnly
+  - ForwardOnlyOpaque
+  - GBufferWithPrepass
+  - TransparentDepthPrepass
   m_SavedProperties:
     serializedVersion: 3
     m_TexEnvs:
     - _DetailAlbedoScale: 1
     - _DetailNormalScale: 1
     - _DetailSmoothnessScale: 1
+    - _DistortionBlendMode: 0
+    - _DistortionBlurBlendMode: 0
+    - _DistortionBlurDstBlend: 1
+    - _DistortionBlurScale: 1
+    - _DistortionBlurSrcBlend: 1
+    - _DistortionDstBlend: 1
+    - _DistortionScale: 1
+    - _DistortionSrcBlend: 1
     - _DistortionStencilRef: 4
     - _DoubleSidedEnable: 0
     - _DoubleSidedNormalMode: 1

SampleScenes/HDTest/GraphicTest/Common/Material/Mat_Distorsion_Unlit_Reject.mat

   - DepthOnly
   - MOTIONVECTORS
   - Forward
+  - ForwardOnlyOpaqueDepthOnly
+  - ForwardOnlyOpaque
+  - GBufferWithPrepass
+  - TransparentDepthPrepass
   m_SavedProperties:
     serializedVersion: 3
     m_TexEnvs:
     - _DetailAlbedoScale: 1
     - _DetailNormalScale: 1
     - _DetailSmoothnessScale: 1
+    - _DistortionBlendMode: 1
+    - _DistortionBlurBlendMode: 0
+    - _DistortionBlurDstBlend: 0
+    - _DistortionBlurScale: 0
+    - _DistortionBlurSrcBlend: 7
+    - _DistortionDstBlend: 0
+    - _DistortionScale: 0
+    - _DistortionSrcBlend: 2
     - _DistortionStencilRef: 0
     - _DoubleSidedEnable: 0
     - _DoubleSidedNormalMode: 1

SampleScenes/HDTest/GraphicTest/Common/Material/Mat_Fire.mat

     - _DetailAlbedoScale: 1
     - _DetailNormalScale: 1
     - _DetailSmoothnessScale: 1
-    - _DistortionBlendMode: 0
+    - _DistortionBlendMode: 1
-    - _DistortionBlurSrcBlend: 0
+    - _DistortionBlurSrcBlend: 7
-    - _DistortionDstBlend: 1
+    - _DistortionDstBlend: 0
-    - _DistortionSrcBlend: 1
+    - _DistortionSrcBlend: 2
     - _DistortionStencilRef: 4
     - _DoubleSidedEnable: 0
     - _DoubleSidedNormalMode: 1

ScriptableRenderPipeline/HDRenderPipeline/HDRenderPipeline.cs

                 cmd.SetComputeTextureParam(resources.applyDistortionCS, resources.applyDistortionKernel, HDShaderIDs._DistortionTexture, m_DistortionBufferRT);
                 cmd.SetComputeTextureParam(resources.applyDistortionCS, resources.applyDistortionKernel, HDShaderIDs._GaussianPyramidColorTexture, m_GaussianPyramidColorBufferRT);
                 cmd.SetComputeTextureParam(resources.applyDistortionCS, resources.applyDistortionKernel, HDShaderIDs._CameraColorTexture, m_CameraColorBufferRT);
+                cmd.SetComputeTextureParam(resources.applyDistortionCS, resources.applyDistortionKernel, HDShaderIDs._DepthTexture, GetDepthTexture());
+                cmd.SetComputeVectorParam(resources.applyDistortionCS, HDShaderIDs._ZBufferParams, Shader.GetGlobalVector(HDShaderIDs._ZBufferParams));
                 cmd.SetComputeVectorParam(resources.applyDistortionCS, HDShaderIDs._GaussianPyramidColorMipSize, Shader.GetGlobalVector(HDShaderIDs._GaussianPyramidColorMipSize));
                 cmd.DispatchCompute(resources.applyDistortionCS, resources.applyDistortionKernel, (int)(size.x) / (int)x, (int)(size.y) / (int)y, 1);
             }

ScriptableRenderPipeline/HDRenderPipeline/Material/Builtin/BuiltinData.hlsl

     velocity = inBuffer.xy;
 }
 
-void EncodeDistortion(float2 distortion, float distortionBlur, bool validSourceForDistortion, out float4 outBuffer)
+void EncodeDistortion(float2 distortion, float distortionBlur, float depthRaw, out float4 outBuffer)
-    // Tag pixel as a pixel that can be used as source for distortion (b != 0)
-    // It is compatible with Add blend mode (a pixel cannot be a valid distortion source only if there is no distorting object in front of it)
-    outBuffer = float4(distortion, validSourceForDistortion ? 1.0 : 0.0, distortionBlur);
+    outBuffer = float4(distortion, depthRaw, distortionBlur);
-void DecodeDistortion(float4 inBuffer, out float2 distortion, out float2 distortionBlur, out bool validSourceForDistortion)
+void DecodeDistortion(float4 inBuffer, out float2 distortion, out float2 distortionBlur, out float depthRaw)
-    validSourceForDistortion = inBuffer.z != 0.0;
+    depthRaw = inBuffer.z;
 }
 
 void GetBuiltinDataDebug(uint paramId, BuiltinData builtinData, inout float3 result, inout bool needLinearToSRGB)

ScriptableRenderPipeline/HDRenderPipeline/RenderPipelineResources/ApplyDistorsion.compute

 #include "../../Core/ShaderLibrary/Common.hlsl"
 #include "../Material/Builtin/BuiltinData.hlsl"
 
-#define DISTORTIONENABLED_STENCILBIT 4
-
-Texture2D<float4> _DistortionTexture;
-Texture2D<float4> _GaussianPyramidColorTexture;
-RWTexture2D<float4> _CameraColorTexture;
+TEXTURE2D(_DepthTexture);
+TEXTURE2D(_DistortionTexture);
+TEXTURE2D(_GaussianPyramidColorTexture);
+RW_TEXTURE2D(float4, _CameraColorTexture);
 
 SamplerState sampler_GaussianPyramidColorTexture;
 
     const float _FetchBias = 0.9;
 
     // Get distortion values
-    float4 encodedDistortion = _DistortionTexture.Load(int3(dispatchThreadId, 0));
+    float4 encodedDistortion = LOAD_TEXTURE2D(_DistortionTexture, dispatchThreadId);
-    bool validForDistortion;
-    DecodeDistortion(encodedDistortion, distortion, distortionBlur, validForDistortion);
+    float depthRaw;
+    DecodeDistortion(encodedDistortion, distortion, distortionBlur, depthRaw);
-    // Get distortion source pixel mask (stored in _DistortionTexture.z)
+    // Discard pixels that are in front of the distortion object
+    float distordedDepth = LOAD_TEXTURE2D(_DepthTexture, distortedEncodedDistortionId).r;
+
+    /*if (distordedDepth > depthRaw)
+        return;*/
+
-    bool distordedValidForDistortion;
-    float4 encodedDistordedDistortion = _DistortionTexture.Load(int3(distortedEncodedDistortionId, 0));
-    DecodeDistortion(encodedDistordedDistortion, distordedDistortion, distordedDistortionBlur, distordedValidForDistortion);
+    float distordedObjectDepth;
+    float4 encodedDistordedDistortion = LOAD_TEXTURE2D(_DistortionTexture, distortedEncodedDistortionId);
+    DecodeDistortion(encodedDistordedDistortion, distordedDistortion, distordedDistortionBlur, distordedObjectDepth);
-    float4 sampled = _GaussianPyramidColorTexture.SampleLevel(sampler_GaussianPyramidColorTexture, distordedUV, mip);
+    float4 sampled = SAMPLE_TEXTURE2D_LOD(_GaussianPyramidColorTexture, sampler_GaussianPyramidColorTexture, distordedUV, mip);
 
     _CameraColorTexture[dispatchThreadId] = sampled;
 }

ScriptableRenderPipeline/HDRenderPipeline/ShaderPass/ShaderPassDistortion.hlsl

     GetSurfaceAndBuiltinData(input, V, posInput, surfaceData, builtinData);
 
     float4 outBuffer;
-    // We do not use pixel outside of distorted objects, so we use masking to reject invalid pixels
-    // https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter19.html (refraction mask)
-    // true = tag this pixel as a valid distortion pixel source
-    EncodeDistortion(builtinData.distortion, builtinData.distortionBlur, true, outBuffer);
+    EncodeDistortion(builtinData.distortion, builtinData.distortionBlur, posInput.depthRaw, outBuffer);
     return outBuffer;
 }