Renamed opacity mask to transmittance mask

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.cs

             public Vector3 transmittanceColor;
             [SurfaceDataAttributes("Transmittance Absorption Distance")]
             public float atDistance;
-            [SurfaceDataAttributes("Opacity mask")]
-            public float opacityMask;
+            [SurfaceDataAttributes("Transmittance mask")]
+            public float transmittanceMask;
         };
 
         //-----------------------------------------------------------------------------
             public float ior;
             // Reuse thickness from SSS
             public Vector3 absorptionCoefficient;
-            public float opacityMask;
+            public float transmittanceMask;
         };
 
         //-----------------------------------------------------------------------------

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.cs.hlsl

 #define DEBUGVIEW_LIT_SURFACEDATA_IOR (1016)
 #define DEBUGVIEW_LIT_SURFACEDATA_TRANSMITTANCE_COLOR (1017)
 #define DEBUGVIEW_LIT_SURFACEDATA_AT_DISTANCE (1018)
-#define DEBUGVIEW_LIT_SURFACEDATA_OPACITY_MASK (1019)
+#define DEBUGVIEW_LIT_SURFACEDATA_TRANSMITTANCE_MASK (1019)
 
 //
 // UnityEngine.Experimental.Rendering.HDPipeline.Lit+BSDFData:  static fields
 #define DEBUGVIEW_LIT_BSDFDATA_COAT_IOR (1050)
 #define DEBUGVIEW_LIT_BSDFDATA_IOR (1051)
 #define DEBUGVIEW_LIT_BSDFDATA_ABSORPTION_COEFFICIENT (1052)
-#define DEBUGVIEW_LIT_BSDFDATA_OPACITY_MASK (1053)
+#define DEBUGVIEW_LIT_BSDFDATA_TRANSMITTANCE_MASK (1053)
 
 //
 // UnityEngine.Experimental.Rendering.HDPipeline.Lit+GBufferMaterial:  static fields
     float ior;
     float3 transmittanceColor;
     float atDistance;
-    float opacityMask;
+    float transmittanceMask;
 };
 
 // Generated from UnityEngine.Experimental.Rendering.HDPipeline.Lit+BSDFData
     float coatIOR;
     float ior;
     float3 absorptionCoefficient;
-    float opacityMask;
+    float transmittanceMask;
 };
 
 //
         case DEBUGVIEW_LIT_SURFACEDATA_AT_DISTANCE:
             result = surfacedata.atDistance.xxx;
             break;
-        case DEBUGVIEW_LIT_SURFACEDATA_OPACITY_MASK:
-            result = surfacedata.opacityMask.xxx;
+        case DEBUGVIEW_LIT_SURFACEDATA_TRANSMITTANCE_MASK:
+            result = surfacedata.transmittanceMask.xxx;
             break;
     }
 }
         case DEBUGVIEW_LIT_BSDFDATA_ABSORPTION_COEFFICIENT:
             result = bsdfdata.absorptionCoefficient;
             break;
-        case DEBUGVIEW_LIT_BSDFDATA_OPACITY_MASK:
-            result = bsdfdata.opacityMask.xxx;
+        case DEBUGVIEW_LIT_BSDFDATA_TRANSMITTANCE_MASK:
+            result = bsdfdata.transmittanceMask.xxx;
             break;
     }
 }

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl

     bsdfData.coatCoverage = coatCoverage;
 }
 
-void FillMaterialIdTransparencyData(float ior, float3 transmittanceColor, float atDistance, float thickness, float opacityMask, inout BSDFData bsdfData)
+void FillMaterialIdTransparencyData(float ior, float3 transmittanceColor, float atDistance, float thickness, float transmittanceMask, inout BSDFData bsdfData)
-    bsdfData.opacityMask = opacityMask;
+    bsdfData.transmittanceMask = transmittanceMask;
     bsdfData.thickness = max(thickness, 0.0001);
 }
 
 #if HAS_REFRACTION
     // Note: Will override thickness of SSS's property set
     FillMaterialIdTransparencyData(
-        surfaceData.ior, surfaceData.transmittanceColor, surfaceData.atDistance, surfaceData.thickness, surfaceData.opacityMask,
+        surfaceData.ior, surfaceData.transmittanceColor, surfaceData.atDistance, surfaceData.thickness, surfaceData.transmittanceMask,
         bsdfData);
 #endif
 
     //    a. Get the corresponding color depending on the roughness from the gaussian pyramid of the color buffer
     //    b. Multiply by the transmittance for absorption (depends on the optical depth)
 
-    weight.x = bsdfData.opacityMask;
+    weight.x = bsdfData.transmittanceMask;
 
     float3 refractedBackPointWS = float3(0.0, 0.0, 0.0);
     float opticalDepth = 0.0;

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitData.hlsl

     surfaceData.ior = 1.0;
     surfaceData.transmittanceColor = float3(1.0, 1.0, 1.0);
     surfaceData.atDistance = 1000000.0;
-    surfaceData.opacityMask = 1.0;
+    surfaceData.transmittanceMask = 1.0;
 
     GetNormalWS(input, V, normalTS, surfaceData.normalWS);
     // Use bent normal to sample GI if available

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitDataInternal.hlsl

     surfaceData.atDistance = _ATDistance;
     // Thickness already defined with SSS (from both thickness and thicknessMap)
     surfaceData.thickness *= _ThicknessMultiplier;
-    // Rough refraction don't use opacity. Instead we use opacity as a opacity mask. 
-    surfaceData.opacityMask = 1.0 - alpha;
+    // Rough refraction don't use opacity. Instead we use opacity as a transmittance mask. 
+    surfaceData.transmittanceMask = 1.0 - alpha;
-    surfaceData.opacityMask = 1.0;
+    surfaceData.transmittanceMask = 1.0;
 #endif
 
     surfaceData.coatNormalWS    = input.worldToTangent[2].xyz; // Assign vertex normal
     surfaceData.ior = 1.0;
     surfaceData.transmittanceColor = float3(1.0, 1.0, 1.0);
     surfaceData.atDistance = 1000000.0;
-    surfaceData.opacityMask = 1.0;
+    surfaceData.transmittanceMask = 1.0;
 
 #endif // #if !defined(LAYERED_LIT_SHADER)