HDRenderPipeline: Add stencil readmask where it make sense

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

             }
             // As we tag both during velocity pass and Gbuffer pass we need a separate state and we need to use the write mask
             material.SetInt(kStencilRef, stencilRef);
-            material.SetInt(kStencilWriteMask, (int)HDRenderPipeline.StencilBitMask.Lighting);
+            material.SetInt(kStencilWriteMask, (int)HDRenderPipeline.StencilBitMask.LightingMask);
             material.SetInt(kStencilRefMV, (int)HDRenderPipeline.StencilBitMask.ObjectVelocity);
             material.SetInt(kStencilWriteMaskMV, (int)HDRenderPipeline.StencilBitMask.ObjectVelocity);
 

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDRenderPipeline.cs

         public enum StencilBitMask
         {
             Clear    = 0,                    // 0x0
-            Lighting = 7,                    // 0x7  - 3 bit
+            LightingMask = 7,                    // 0x7  - 3 bit
             ObjectVelocity = 128,            // 1 bit
             All      = 255                   // 0xFF - 8 bit
         }
             // General material
             m_CopyStencilForNoLighting = CoreUtils.CreateEngineMaterial(asset.renderPipelineResources.copyStencilBuffer);
             m_CopyStencilForNoLighting.SetInt(HDShaderIDs._StencilRef, (int)StencilLightingUsage.NoLighting);
+            m_CopyStencilForNoLighting.SetInt(HDShaderIDs._StencilMask, (int)StencilBitMask.LightingMask);
             m_CameraMotionVectorsMaterial = CoreUtils.CreateEngineMaterial(asset.renderPipelineResources.cameraMotionVectors);
 
             InitializeDebugMaterials();
                                 // In the material classification shader we will simply test is we are no lighting
                                 // Use ShaderPassID 1 => "Pass 1 - Write 1 if value different from stencilRef to output"
                                 CoreUtils.DrawFullScreen(cmd, m_CopyStencilForNoLighting, m_CameraStencilBufferCopyRT, m_CameraDepthStencilBufferRT, null, 1);
-                                cmd.ClearRandomWriteTargets();
                             }
                         }
 

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDStringConstants.cs

         public static readonly int _ProjectionParams = Shader.PropertyToID("_ProjectionParams");
         public static readonly int _WorldSpaceCameraPos = Shader.PropertyToID("_WorldSpaceCameraPos");
 
+        public static readonly int _StencilMask = Shader.PropertyToID("_StencilMask");
         public static readonly int _StencilRef = Shader.PropertyToID("_StencilRef");
         public static readonly int _StencilCmp = Shader.PropertyToID("_StencilCmp");
 

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/SubsurfaceScattering/CombineLighting.shader

 Shader "Hidden/HDRenderPipeline/CombineLighting"
 {
+    Properties
+    {
+        [HideInInspector] _StencilMask("_StencilMask", Int) = 7
+    }
+
+    HLSLINCLUDE
+
+    int _StencilMask;
+
+    ENDHLSL
+
+
     SubShader
     {
         Pass
+                ReadMask [_StencilMask]
                 Ref  1 // StencilLightingUsage.SplitLighting
                 Comp Equal
                 Pass Keep

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/SubsurfaceScattering/SubsurfaceScatteringManager.cs

             m_SubsurfaceScatteringCS = hdAsset.renderPipelineResources.subsurfaceScatteringCS;
             m_SubsurfaceScatteringKernel = m_SubsurfaceScatteringCS.FindKernel("SubsurfaceScattering");
             m_CombineLightingPass = CoreUtils.CreateEngineMaterial(hdAsset.renderPipelineResources.combineLighting);
+            m_CombineLightingPass.SetInt(HDShaderIDs._StencilMask, (int)HDRenderPipeline.StencilBitMask.LightingMask);
 
             // Jimenez SSS Model (shader)
             m_SssVerticalFilterPass = CoreUtils.CreateEngineMaterial(hdAsset.renderPipelineResources.subsurfaceScattering);
 
             m_CopyStencilForSplitLighting = CoreUtils.CreateEngineMaterial(hdAsset.renderPipelineResources.copyStencilBuffer);
             m_CopyStencilForSplitLighting.SetInt(HDShaderIDs._StencilRef, (int)StencilLightingUsage.SplitLighting);
+            m_CopyStencilForSplitLighting.SetInt(HDShaderIDs._StencilMask, (int)HDRenderPipeline.StencilBitMask.LightingMask);
         }
 
         public void Cleanup()

ScriptableRenderPipeline/HDRenderPipeline/HDRP/RenderPipelineResources/CopyStencilBuffer.shader

     Properties
     {
         [HideInInspector] _StencilRef("_StencilRef", Int) = 1
+        [HideInInspector] _StencilMask("_StencilMask", Int) = 7
     }
 
     HLSLINCLUDE
     #include "../Lighting/LightDefinition.cs.hlsl"
 
     int _StencilRef;
+    int _StencilMask;
     RW_TEXTURE2D(float, _HTile); // DXGI_FORMAT_R8_UINT is not supported by Unity
 
     struct Attributes
 
             Stencil
             {
+                ReadMask [_StencilMask]
                 Ref  [_StencilRef]
                 Comp Equal
                 Pass Keep
 
             Stencil
             {
+                ReadMask [_StencilMask]
                 Ref  [_StencilRef]
                 Comp NotEqual
                 Pass Keep
 
             Stencil
             {
+                ReadMask [_StencilMask]
                 Ref  [_StencilRef]
                 Comp Equal
                 Pass Keep