Add blending support for the tessellation shader

Assets/ScriptableRenderLoop/HDRenderPipeline/HDRenderPipeline.cs

             m_CombineSubsurfaceScattering.SetFloat("_BilateralScale", 0.05f * sssParameters.bilateralScale);
             // TODO: use user-defined values for '_ProfileID' and '_FilterRadius.'
             m_CombineSubsurfaceScattering.SetVectorArray("_FilterKernel", sssParameters.profiles[0].filterKernel);
-            m_CombineSubsurfaceScattering.SetFloat("_FilterRadius", 5.0f);
+            m_CombineSubsurfaceScattering.SetFloat("_FilterRadius", 3.0f);
 
             MaterialPropertyBlock properties = new MaterialPropertyBlock();
 

Assets/ScriptableRenderLoop/HDRenderPipeline/Material/Lit/Editor/BaseLitUI.cs

             
             public static GUIContent detailMapModeText = new GUIContent("Detail Map with Normal", "Detail Map with AO / Height");
             public static GUIContent UVDetailMappingText = new GUIContent("UV set for Detail", "");
-            public static GUIContent subsurfaceScatteringText = new GUIContent("Subsurface Scattering", "Enable for translucent materials such as skin, vegetation, fruit, marble, wax and milk");
+            public static GUIContent materialClassText = new GUIContent("Material Class", "Subsurface Scattering: enable for translucent materials such as skin, vegetation, fruit, marble, wax and milk.");
             public static GUIContent emissiveColorModeText = new GUIContent("Emissive Color Usage", "Use emissive color or emissive mask");
 
             public static string InputsText = "Inputs";
             Phong,
             Displacement,
             DisplacementPhong,
+        }
+
+        public enum MaterialClass
+        {
+            Standard,
+            SSS,
+            Hair
         }
 
         void SurfaceTypePopup()

Assets/ScriptableRenderLoop/HDRenderPipeline/Material/Lit/Editor/LitUI.cs

             UseEmissiveMask,
         }
 
-        public enum SubsurfaceScattering
-        {
-            Disabled,
-            Enabled
-        }
-
         protected MaterialProperty smoothnessMapChannel = null;
         protected const string kSmoothnessTextureChannel = "_SmoothnessTextureChannel";
         protected MaterialProperty UVBase = null;
         protected const string kUVDetail = "_UVDetail";
         protected MaterialProperty UVDetailsMappingMask = null;
         protected const string kUVDetailsMappingMask = "_UVDetailsMappingMask";
-        protected MaterialProperty subsurfaceScattering = null;
-        protected const string kSubsurfaceScattering = "_SubsurfaceScattering";
+        protected MaterialProperty materialClass = null;
+        protected const string kMaterialClass = "_MaterialClass";
         protected MaterialProperty emissiveColorMode = null;
         protected const string kEmissiveColorMode = "_EmissiveColorMode";
 
             ppdMinSamples = FindProperty(kPpdMinSamples, props);
             ppdMaxSamples = FindProperty(kPpdMaxSamples, props);
             detailMapMode = FindProperty(kDetailMapMode, props);
-            subsurfaceScattering = FindProperty(kSubsurfaceScattering, props);
+            materialClass = FindProperty(kMaterialClass, props);
             emissiveColorMode = FindProperty(kEmissiveColorMode, props);
         }
 
             m_MaterialEditor.ShaderProperty(ppdMinSamples, Styles.ppdMinSamplesText);
             m_MaterialEditor.ShaderProperty(ppdMaxSamples, Styles.ppdMaxSamplesText);
             ppdMinSamples.floatValue = Mathf.Min(ppdMinSamples.floatValue, ppdMaxSamples.floatValue);
-            m_MaterialEditor.ShaderProperty(subsurfaceScattering, Styles.subsurfaceScatteringText);
+            m_MaterialEditor.ShaderProperty(materialClass, Styles.materialClassText);
             EditorGUI.indentLevel--;
         }
 
 			SetKeyword(material, "_ANISOTROPYMAP", material.GetTexture(kAnisotropyMap));
 			SetKeyword(material, "_DETAIL_MAP", material.GetTexture(kDetailMap));
 
-            bool enableSSS = material.GetFloat(kSubsurfaceScattering) != 0.0f;
-            material.SetInt("_StencilRef", (int)(enableSSS ? StencilBits.SSS : StencilBits.None));
-
             bool needUV2 = (UVDetailMapping)material.GetFloat(kUVDetail) == UVDetailMapping.UV2 && (UVBaseMapping)material.GetFloat(kUVBase) == UVBaseMapping.UV0;
             bool needUV3 = (UVDetailMapping)material.GetFloat(kUVDetail) == UVDetailMapping.UV3 && (UVBaseMapping)material.GetFloat(kUVBase) == UVBaseMapping.UV0;
 
                 material.DisableKeyword("_REQUIRE_UV2");
                 material.DisableKeyword("_REQUIRE_UV3");
             }
+
+            material.SetInt("_StencilRef", (int)material.GetFloat(kMaterialClass)); // See 'StencilBits'.
          }
     }
 } // namespace UnityEditor

Assets/ScriptableRenderLoop/HDRenderPipeline/Material/Lit/Lit.shader

         _DetailHeightScale("_DetailHeightScale", Range(-2.0, 2.0)) = 1
         _DetailAOScale("_DetailAOScale", Range(-2.0, 2.0)) = 1
 
-        [ToggleOff] _SubsurfaceScattering("Subsurface Scattering", Int) = 0
+        [Enum(Standard, 0, Subsurface Scattering, 1, Hair, 2)] _MaterialClass("Material Class", Int) = 0
         _SubSurfaceRadius("SubSurfaceRadius", Range(0.0, 1.0)) = 0
         _SubSurfaceRadiusMap("SubSurfaceRadiusMap", 2D) = "white" {}
         //_Thickness("Thickness", Range(0.0, 1.0)) = 0

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

     // This part of the code is not used in case of layered shader but we keep the same macro system for simplicity
 #if !defined(LAYERED_LIT_SHADER)
 
-    surfaceData.materialId = 0; // TODO
+    surfaceData.materialId = _MaterialClass;
 
     // TODO: think about using BC5
 #ifdef _TANGENTMAP

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

 TEXTURE2D(_AnisotropyMap);
 SAMPLER2D(sampler_AnisotropyMap);
 
+float _MaterialClass;
+
 //float _SubSurfaceRadius;
 //TEXTURE2D(_SubSurfaceRadiusMap);
 //SAMPLER2D(sampler_SubSurfaceRadiusMap);

Assets/ScriptableRenderLoop/HDRenderPipeline/Material/Lit/LitTessellation.shader

         _DetailHeightScale("_DetailHeightScale", Range(-2.0, 2.0)) = 1
         _DetailAOScale("_DetailAOScale", Range(-2.0, 2.0)) = 1        
 
+		[Enum(Standard, 0, Subsurface Scattering, 1, Hair, 2)] _MaterialClass("Material Class", Int) = 0
         _SubSurfaceRadius("SubSurfaceRadius", Range(0.0, 1.0)) = 0
         _SubSurfaceRadiusMap("SubSurfaceRadiusMap", 2D) = "white" {}
         //_Thickness("Thickness", Range(0.0, 1.0)) = 0
 
         [ToggleOff]  _AlphaCutoffEnable("Alpha Cutoff Enable", Float) = 0.0
         _AlphaCutoff("Alpha Cutoff", Range(0.0, 1.0)) = 0.5
+
+		// Stencil state
+        [HideInInspector] _StencilRef("_StencilRef", Int) = 0
 
         // Blending state
         [HideInInspector] _SurfaceType("__surfacetype", Float) = 0.0
             Tags { "LightMode" = "GBuffer" } // This will be only for opaque object based on the RenderQueue index
 
             Cull  [_CullMode]
+
+			Stencil
+            {
+                Ref  [_StencilRef]
+                Comp Always
+                Pass Replace
+            }
 
             HLSLPROGRAM
 

Assets/ScriptableRenderLoop/HDRenderPipeline/Material/Lit/Resources/CombineSubsurfaceScattering.shader

 
             HLSLPROGRAM
             #pragma target 4.5
-            #pragma only_renderers d3d11 ps4 metal // TEMP: unitl we go futher in dev
+            #pragma only_renderers d3d11 ps4 metal // TEMP: until we go further in dev
 
             #pragma vertex Vert
             #pragma fragment Frag

Assets/ScriptableRenderLoop/HDRenderPipeline/Utilities.cs

     [Flags]
     public enum StencilBits
     {
-        None = 0,
-        SSS  = 1,
-        All  = 255
+        None = 0,  
+        SSS  = 1,  // BaseLitGUI.MaterialClass.SSS
+        Hair = 2,  // BaseLitGUI.MaterialClass.Hair
+        All  = 255 // 0xff
     }
 
     public class Utilities