Add an option to oversample SSS in the settings

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/RenderLoopSettings/RenderPipelineSettingsUI.cs

             EditorGUILayout.PropertyField(d.supportForwardOnly, _.GetContent("Support Forward Only"));
             EditorGUILayout.PropertyField(d.supportMotionVectors, _.GetContent("Support Motion Vectors"));
             EditorGUILayout.PropertyField(d.supportStereo, _.GetContent("Support Stereo Rendering"));
+            EditorGUILayout.PropertyField(d.enableUltraQualitySSS, _.GetContent("Enable Ultra Quality SSS"));
             --EditorGUI.indentLevel;
         }
     }

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/RenderLoopSettings/SerializedRenderPipelineSettings.cs

         public SerializedProperty supportForwardOnly;
         public SerializedProperty supportMotionVectors;
         public SerializedProperty supportStereo;
+        public SerializedProperty enableUltraQualitySSS;
 
         public SerializedGlobalLightLoopSettings lightLoopSettings;
         public SerializedShadowInitParameters shadowInitParams;
             supportForwardOnly = root.Find((RenderPipelineSettings s) => s.supportForwardOnly);
             supportMotionVectors = root.Find((RenderPipelineSettings s) => s.supportMotionVectors);
             supportStereo = root.Find((RenderPipelineSettings s) => s.supportStereo);
+            enableUltraQualitySSS = root.Find((RenderPipelineSettings s) => s.enableUltraQualitySSS);
 
             lightLoopSettings = new SerializedGlobalLightLoopSettings(root.Find((RenderPipelineSettings s) => s.lightLoopSettings));
             shadowInitParams = new SerializedShadowInitParameters(root.Find((RenderPipelineSettings s) => s.shadowInitParams));

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/SubsurfaceScattering/SubsurfaceScattering.compute

 // Definitions
 //--------------------------------------------------------------------------------------------------
 
+#pragma kernel SubsurfaceScatteringQualityNormal SubsurfaceScattering=SubsurfaceScatteringQualityNormal SSS_ENABLE_NEAR_FIELD=0
+#pragma kernel SubsurfaceScatteringQualityUltra  SubsurfaceScattering=SubsurfaceScatteringQualityUltra  SSS_ENABLE_NEAR_FIELD=1
+
 // #pragma enable_d3d11_debug_symbols
 // TODO: use sharp load hoisting on PS4.
 
 #define SSS_RANDOM_ROTATION   1 // Hides undersampling artifacts with high-frequency noise. TAA blurs the noise.
-#define SSS_ENABLE_NEAR_FIELD 0 // Greatly increases the number of samples. Comes at a high cost.
 #define SSS_USE_TANGENT_PLANE 0 // Improves the accuracy of the approximation(0 -> 1st order). High cost. Does not work with back-facing normals.
 #define SSS_CLAMP_ARTIFACT    0 // Reduces bleeding. Use with SSS_USE_TANGENT_PLANE.
 #define SSS_DEBUG_LOD         0
     _CameraColorTexture[pixelCoord]    += float4(irradiance, 0);
 #endif
 }
-
-#pragma kernel SubsurfaceScattering
 
 [numthreads(GROUP_SIZE_2D, 1, 1)]
 void SubsurfaceScattering(uint2 groupId       : SV_GroupID,

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

         public void Build(HDRenderPipelineAsset hdAsset)
         {
             // Disney SSS (compute + combine)
+            string kernelName = hdAsset.renderPipelineSettings.enableUltraQualitySSS ? "SubsurfaceScatteringQualityUltra" : "SubsurfaceScatteringQualityNormal";
-            m_SubsurfaceScatteringKernel = m_SubsurfaceScatteringCS.FindKernel("SubsurfaceScattering");
+            m_SubsurfaceScatteringKernel = m_SubsurfaceScatteringCS.FindKernel(kernelName);
             m_CombineLightingPass = CoreUtils.CreateEngineMaterial(hdAsset.renderPipelineResources.combineLighting);
             m_CombineLightingPass.SetInt(HDShaderIDs._StencilMask, (int)HDRenderPipeline.StencilBitMask.LightingMask);
 

ScriptableRenderPipeline/HDRenderPipeline/HDRP/RenderPipeline/RenderPipelineSettings.cs

         public bool supportSSAO = true;
         public bool supportSubsurfaceScattering = true;
         public bool supportForwardOnly = false;
+        public bool enableUltraQualitySSS = false;
 
         // Engine
         public bool         supportDBuffer = false;