Add transmittance preview

Assets/ScriptableRenderPipeline/HDRenderPipeline/SceneSettings/Resources/DrawGaussianProfile.shader

             Varyings Vert(Attributes input)
             {
                 Varyings output;
-                output.vertex = TransformWorldToHClip(input.vertex);
+                output.vertex   = TransformWorldToHClip(input.vertex);
                 output.texcoord = input.texcoord.xy;
                 return output;
             }

Assets/ScriptableRenderPipeline/HDRenderPipeline/SceneSettings/SubsurfaceScatteringParameters.cs

         {
             public readonly GUIContent category              = new GUIContent("Subsurface scattering parameters");
             public readonly GUIContent[] profiles            = new GUIContent[SubsurfaceScatteringParameters.maxNumProfiles] { new GUIContent("Profile #0"), new GUIContent("Profile #1"), new GUIContent("Profile #2"), new GUIContent("Profile #3"), new GUIContent("Profile #4"), new GUIContent("Profile #5"), new GUIContent("Profile #6"), new GUIContent("Profile #7") };
-            public readonly GUIContent profilePreview        = new GUIContent("Profile preview. Note that the intensity of the region in the center may be clamped.");
+            public readonly GUIContent profilePreview0       = new GUIContent("Profile preview");
+            public readonly GUIContent profilePreview1       = new GUIContent("Shows the fraction of light scattered from the source as radius increases to 1.");
+            public readonly GUIContent profilePreview2       = new GUIContent("Note that the intensity of the region in the center may be clamped.");
+            public readonly GUIContent transmittancePreview0 = new GUIContent("Transmittance preview");
+            public readonly GUIContent transmittancePreview1 = new GUIContent("Shows the fraction of light passing through the object as thickness increases to 1.");
             public readonly GUIContent numProfiles           = new GUIContent("Number of profiles");
             public readonly GUIContent profileStdDev1        = new GUIContent("Standard deviation #1", "Determines the shape of the 1st Gaussian filter. Increases the strength and the radius of the blur of the corresponding color channel.");
             public readonly GUIContent profileStdDev2        = new GUIContent("Standard deviation #2", "Determines the shape of the 2nd Gaussian filter. Increases the strength and the radius of the blur of the corresponding color channel.");
+
+            public readonly GUIStyle   centeredMiniBoldLabel = new GUIStyle (GUI.skin.label);
-        private Material           m_ProfileMaterial;
-        private RenderTexture[]    m_ProfileImages;
+        private Material           m_ProfileMaterial, m_TransmittanceMaterial;
+        private RenderTexture[]    m_ProfileImages, m_TransmittanceImages;
 
         // --- Public Methods ---
 
                 {
                     s_Styles = new Styles();
                 }
+
+                s_Styles.centeredMiniBoldLabel.alignment = TextAnchor.MiddleCenter;
+                s_Styles.centeredMiniBoldLabel.fontSize  = 10;
+                s_Styles.centeredMiniBoldLabel.fontStyle = FontStyle.Bold;
+
                 return s_Styles;
             }
         }
-            m_EnableSSS       = serializedObject.FindProperty("m_EnableSSS");
-            m_Profiles        = serializedObject.FindProperty("m_Profiles");
-            m_NumProfiles     = m_Profiles.FindPropertyRelative("Array.size");
-            m_ProfileMaterial = Utilities.CreateEngineMaterial("Hidden/HDRenderPipeline/DrawGaussianProfile");
-            m_ProfileImages   = new RenderTexture[SubsurfaceScatteringParameters.maxNumProfiles];
+            m_EnableSSS             = serializedObject.FindProperty("m_EnableSSS");
+            m_Profiles              = serializedObject.FindProperty("m_Profiles");
+            m_NumProfiles           = m_Profiles.FindPropertyRelative("Array.size");
+            m_ProfileMaterial       = Utilities.CreateEngineMaterial("Hidden/HDRenderPipeline/DrawGaussianProfile");
+            m_TransmittanceMaterial = Utilities.CreateEngineMaterial("Hidden/HDRenderPipeline/DrawTransmittanceGraph");
+            m_ProfileImages         = new RenderTexture[SubsurfaceScatteringParameters.maxNumProfiles];
+            m_TransmittanceImages   = new RenderTexture[SubsurfaceScatteringParameters.maxNumProfiles];
-                m_ProfileImages[i] = new RenderTexture(256, 256, 0, RenderTextureFormat.DefaultHDR);
+                m_ProfileImages[i]       = new RenderTexture(256, 256, 0, RenderTextureFormat.DefaultHDR);
+                m_TransmittanceImages[i] = new RenderTexture(16,  256, 0, RenderTextureFormat.DefaultHDR);
             }
         }
 
                         EditorGUILayout.PropertyField(profileThicknessScale, styles.profileThicknessScale);
 
                         EditorGUILayout.Space();
+                        EditorGUILayout.LabelField(styles.profilePreview0, styles.centeredMiniBoldLabel);
+                        EditorGUILayout.LabelField(styles.profilePreview1, EditorStyles.centeredGreyMiniLabel);
+                        EditorGUILayout.LabelField(styles.profilePreview2, EditorStyles.centeredGreyMiniLabel);
+                        EditorGUILayout.Space();
-                        EditorGUI.DrawPreviewTexture(GUILayoutUtility.GetRect(256, 256), m_ProfileImages[i], m_ProfileMaterial, ScaleMode.ScaleToFit);
+                        EditorGUI.DrawPreviewTexture(GUILayoutUtility.GetRect(256, 256), m_ProfileImages[i], m_ProfileMaterial, ScaleMode.ScaleToFit, 1.0f);
-                        EditorGUILayout.LabelField(styles.profilePreview, EditorStyles.centeredGreyMiniLabel);
+                        EditorGUILayout.LabelField(styles.transmittancePreview0, styles.centeredMiniBoldLabel);
+                        EditorGUILayout.LabelField(styles.transmittancePreview1, EditorStyles.centeredGreyMiniLabel);
+                        EditorGUILayout.Space();
+
+                        // Draw the transmittance graph.
+                        m_TransmittanceMaterial.SetColor("_StdDev1",        profileStdDev1.colorValue);
+                        m_TransmittanceMaterial.SetColor("_StdDev2",        profileStdDev2.colorValue);
+                        m_TransmittanceMaterial.SetFloat("_LerpWeight",     profileLerpWeight.floatValue);
+                        m_TransmittanceMaterial.SetFloat("_ThicknessScale", profileThicknessScale.floatValue);
+                        EditorGUI.DrawPreviewTexture(GUILayoutUtility.GetRect(16, 16), m_TransmittanceImages[i], m_TransmittanceMaterial, ScaleMode.ScaleToFit, 16.0f);
+
                         EditorGUILayout.Space();
 
                         EditorGUI.indentLevel--;

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

+Shader "Hidden/HDRenderPipeline/DrawTransmittanceGraph"
+{
+    Properties
+    {
+        [HideInInspector] _StdDev1("", Color) = (0, 0, 0)
+        [HideInInspector] _StdDev2("", Color) = (0, 0, 0)
+        [HideInInspector] _LerpWeight("", Float) = 0
+        [HideInInspector] _ThicknessScale("", Float) = 0
+    }
+
+    SubShader
+    {
+        Pass
+        {
+            Cull   Off
+            ZTest  Off
+            ZWrite Off
+            Blend  Off
+
+            HLSLPROGRAM
+            #pragma target 4.5
+            #pragma only_renderers d3d11 ps4 metal // TEMP: until we go further in dev
+
+            #pragma vertex Vert
+            #pragma fragment Frag
+
+            //-------------------------------------------------------------------------------------
+            // Include
+            //-------------------------------------------------------------------------------------
+
+            #include "ShaderLibrary/Common.hlsl"
+            #include "ShaderLibrary/Color.hlsl"
+            #include "HDRenderPipeline/ShaderVariables.hlsl"
+
+            //-------------------------------------------------------------------------------------
+            // Inputs & outputs
+            //-------------------------------------------------------------------------------------
+
+            float4 _StdDev1, _StdDev2;
+            float _LerpWeight, _ThicknessScale; // See 'SubsurfaceScatteringParameters'
+
+            //-------------------------------------------------------------------------------------
+            // Implementation
+            //-------------------------------------------------------------------------------------
+
+            struct Attributes
+            {
+                float3 vertex   : POSITION;
+                float2 texcoord : TEXCOORD0;
+            };
+
+            struct Varyings
+            {
+                float4 vertex   : SV_POSITION;
+                float2 texcoord : TEXCOORD0;
+            };
+
+            Varyings Vert(Attributes input)
+            {
+                Varyings output;
+                output.vertex   = TransformWorldToHClip(input.vertex);
+                output.texcoord = input.texcoord.xy;
+                return output;
+            }
+
+            float4 Frag(Varyings input) : SV_Target
+            {
+                float thickness = input.texcoord.x * _ThicknessScale;
+                float t2        = thickness * thickness;
+
+                float3 var1 = _StdDev1.rgb * _StdDev1.rgb;
+                float3 var2 = _StdDev2.rgb * _StdDev2.rgb;
+
+                // See ComputeTransmittance() in Lit.hlsl for more details.
+                float3 transmittance = lerp(exp(-t2 * 0.5 * rcp(var1)),
+                                            exp(-t2 * 0.5 * rcp(var2)), _LerpWeight);
+
+                return float4(transmittance, 1);
+            }
+            ENDHLSL
+        }
+    }
+    Fallback Off
+}

Assets/ScriptableRenderPipeline/HDRenderPipeline/SceneSettings/Resources/DrawTransmittanceGraph.shader.meta

+fileFormatVersion: 2
+guid: 4517edda0467bb14489d5eccc9973ba2
+timeCreated: 1487326565
+licenseType: Pro
+ShaderImporter:
+  defaultTextures: []
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: