Change selection of SSS method from dynamic to static

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/Material/SubsurfaceScattering/SubsurfaceScatteringSettingsEditor.Styles.cs

         // TODO: missing tooltips
         sealed class Styles
         {
-            public readonly GUIContent   useDisneySSS              = new GUIContent("Use Disney SSS");
-
             public readonly GUIContent   profilePreview0           = new GUIContent("Profile Preview");
             public readonly GUIContent   profilePreview1           = new GUIContent("Shows the fraction of light scattered from the source (center).");
             public readonly GUIContent   profilePreview2           = new GUIContent("The distance to the boundary of the image corresponds to the Max Radius.");

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/Material/SubsurfaceScattering/SubsurfaceScatteringSettingsEditor.cs

             }
         }
 
-        SerializedProperty m_UseDisneySSS;
         List<Profile> m_Profiles;
 
         Material m_ProfileMaterial;
             int count = SssConstants.SSS_N_PROFILES - 1;
             m_Profiles = new List<Profile>();
 
-            m_UseDisneySSS = properties.Find(x => x.useDisneySSS);
             var serializedProfiles = properties.Find(x => x.profiles);
 
             for (int i = 0; i < count; i++)
 
             serializedObject.Update();
 
-            EditorGUILayout.PropertyField(m_UseDisneySSS, s_Styles.useDisneySSS);
-
-            bool useDisneySSS = m_UseDisneySSS.boolValue;
+            bool useDisneySSS = ShaderConfig.k_UseDisneySSS == 1;
 
             for (int i = 0; i < m_Profiles.Count; i++)
             {

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDRenderPipeline.cs

 
         void Resize(HDCamera hdCamera)
         {
-            var camera = hdCamera.camera;
-
             // TODO: Detect if renderdoc just load and force a resize in this case, as often renderdoc require to realloc resource.
 
             // TODO: This is the wrong way to handle resize/allocation. We can have several different camera here, mean that the loop on camera will allocate and deallocate

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDStringConstants.cs

         public static readonly int _SkyTexture = Shader.PropertyToID("_SkyTexture");
         public static readonly int _SkyTextureMipCount = Shader.PropertyToID("_SkyTextureMipCount");
 
-        public static readonly int _UseDisneySSS = Shader.PropertyToID("_UseDisneySSS");
         public static readonly int _EnableSSSAndTransmission = Shader.PropertyToID("_EnableSSSAndTransmission");
         public static readonly int _TexturingModeFlags = Shader.PropertyToID("_TexturingModeFlags");
         public static readonly int _TransmissionFlags = Shader.PropertyToID("_TransmissionFlags");

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/Lit/Lit.hlsl

         bsdfData.thickness = _ThicknessRemaps[subsurfaceProfile].x + _ThicknessRemaps[subsurfaceProfile].y * thickness;
         bsdfData.useThickObjectMode = transmissionMode != SSS_TRSM_MODE_THIN;
 
-        if (_UseDisneySSS != 0)
-        {
+#if SHADEROPTIONS_USE_DISNEY_SSS
-        }
-        else
-        {
+#else
             bsdfData.transmittance = ComputeTransmittanceJimenez(_HalfRcpVariancesAndWeights[subsurfaceProfile][0].rgb,
                                                                  _HalfRcpVariancesAndWeights[subsurfaceProfile][0].a,
                                                                  _HalfRcpVariancesAndWeights[subsurfaceProfile][1].rgb,
-        }
+#endif
     }
 }
 
         float3 boxOuterDistance = lightData.influenceExtents;
         float projectionDistance = BoxRayIntersectSimple(positionLS, dirLS, -boxOuterDistance, boxOuterDistance);
         projectionDistance = max(projectionDistance, lightData.minProjectionDistance); // Setup projection to infinite if requested (mean no projection shape)
-        
+
         // No need to normalize for fetching cubemap
         // We can reuse dist calculate in LS directly in WS as there is no scaling. Also the offset is already include in lightData.positionWS
         R = (positionWS + projectionDistance * R) - lightData.positionWS;

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/SubsurfaceScattering/SubsurfaceScattering.hlsl

 float  _TexturingModeFlags;       // 1 bit/profile; 0 = PreAndPostScatter, 1 = PostScatter
 float  _TransmissionFlags;        // 2 bit/profile; 0 = inf. thick, 1 = thin, 2 = regular
 // Old SSS Model >>>
-uint   _UseDisneySSS;
 float4 _HalfRcpVariancesAndWeights[SSS_N_PROFILES][2]; // 2x Gaussians in RGB, A is interpolation weights
 // <<< Old SSS Model
 // Use float4 to avoid any packing issue between compute and pixel shaders

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

         {
             // Broadcast SSS parameters to all shaders.
             cmd.SetGlobalInt(HDShaderIDs._EnableSSSAndTransmission, frameSettings.enableSSSAndTransmission ? 1 : 0);
-            cmd.SetGlobalInt(HDShaderIDs._UseDisneySSS, sssParameters.useDisneySSS ? 1 : 0);
             unsafe
             {
                 // Warning: Unity is not able to losslessly transfer integers larger than 2^24 to the shader system.
             using (new ProfilingSample(cmd, "Subsurface Scattering", HDRenderPipeline.GetSampler(CustomSamplerId.SubsurfaceScattering)))
             {
                 // For Jimenez we always need an extra buffer, for Disney it depends on platform
-                if (!sssParameters.useDisneySSS ||
-                    (sssParameters.useDisneySSS && NeedTemporarySubsurfaceBuffer()))
+                if (ShaderConfig.k_UseDisneySSS == 0 ||
+                    ((ShaderConfig.k_UseDisneySSS == 1) && NeedTemporarySubsurfaceBuffer()))
                 {
                     // Caution: must be same format as m_CameraSssDiffuseLightingBuffer
                     cmd.ReleaseTemporaryRT(m_CameraFilteringBuffer);
                     }
                 }
 
-                if (sssParameters.useDisneySSS)
+                if (ShaderConfig.s_UseDisneySSS == 1) // use static here to quiet the compiler warning
                 {
                     using (new ProfilingSample(cmd, "HTile for SSS", HDRenderPipeline.GetSampler(CustomSamplerId.HTileForSSS)))
                     {

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

 
     public sealed class SubsurfaceScatteringSettings : ScriptableObject
     {
-        public bool useDisneySSS = true;
         public SubsurfaceScatteringProfile[] profiles;
 
         [NonSerialized] public uint      texturingModeFlags;        // 1 bit/profile; 0 = PreAndPostScatter, 1 = PostScatter

ScriptableRenderPipeline/HDRenderPipeline/HDRP/SceneSettings/Resources/DrawTransmittanceGraph.shader

             // Inputs & outputs
             //-------------------------------------------------------------------------------------
 
-            uint   _UseDisneySSS;
             float4 _HalfRcpVarianceAndWeight1, _HalfRcpVarianceAndWeight2;
             float4 _ShapeParam, _TransmissionTint, _ThicknessRemap;
 
                 float  d = (_ThicknessRemap.x + input.texcoord.x * (_ThicknessRemap.y - _ThicknessRemap.x));
                 float3 T;
 
-                if (_UseDisneySSS)
-                {
+#if SHADEROPTIONS_USE_DISNEY_SSS
-                }
-                else
-                {
+#else
-                }
+#endif
 
                 // Apply gamma for visualization only. Do not apply gamma to the color.
                 return float4(sqrt(T) * _TransmissionTint.rgb, 1);

ScriptableRenderPipeline/HDRenderPipeline/HDRP/ShaderConfig.cs

     [GenerateHLSL(PackingRules.Exact)]
     public enum ShaderOptions
     {
-        CameraRelativeRendering = 1 // Rendering sets the origin of the world to the position of the primary (scene view) camera
+        CameraRelativeRendering = 1, // Rendering sets the origin of the world to the position of the primary (scene view) camera
+        UseDisneySSS = 1 // Allow to chose between Burley Normalized Diffusion (Multi + Fix single scattering) or Jimenez diffusion approximation (Multiscattering only - More blurry) for Subsurface scattering
     };
 
     // Note: #define can't be use in include file in C# so we chose this way to configure both C# and hlsl
         public const int k_CameraRelativeRendering = (int)ShaderOptions.CameraRelativeRendering;
         public static int s_CameraRelativeRendering = (int)ShaderOptions.CameraRelativeRendering;
+
+        public const int k_UseDisneySSS = (int)ShaderOptions.UseDisneySSS;
+        public static int s_UseDisneySSS = (int)ShaderOptions.UseDisneySSS;
     }
 }

ScriptableRenderPipeline/HDRenderPipeline/HDRP/ShaderConfig.cs.hlsl

 // UnityEngine.Experimental.Rendering.HDPipeline.ShaderOptions:  static fields
 //
 #define SHADEROPTIONS_CAMERA_RELATIVE_RENDERING (1)
+#define SHADEROPTIONS_USE_DISNEY_SSS (1)
 
 
 #endif