HDRenderPipeline: Add basic specular occlusoin support from Ambient occlusion map

ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/TilePass.cs

 
                 Vector3 camPosWS = camera.transform.position;
 
+                // Note: Light with null intensity/Color are culled by the C++, no need to test it here
                 if (cullResults.visibleLights.Count != 0 || cullResults.visibleReflectionProbes.Count != 0)
                 {
                     // 0. deal with shadows

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitData.hlsl

     float alpha = GetSurfaceData(input, layerTexCoord, surfaceData, normalTS, bentNormalTS);
     GetNormalWS(input, V, normalTS, surfaceData.normalWS);
     // Use bent normal to sample GI if available
-    surfaceData.specularOcclusion = 1.0;
-    #ifdef _ENABLESPECULAROCCLUSION
+#else
+    bentNormalWS = surfaceData.normalWS;
+#endif
+
+    // By default we use the ambient occlusion with Tri-ace trick (apply outside) for specular occlusion.
+    // If user provide bent normal then we process a better term
+#if defined(_BENTNORMALMAP) && defined(_ENABLESPECULAROCCLUSION)
-    #endif
+#elif defined(_MASKMAP)
+    surfaceData.specularOcclusion = GetSpecularOcclusionFromAmbientOcclusion(dot(surfaceData.normalWS, V), surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
-    bentNormalWS = surfaceData.normalWS;
+    surfaceData.specularOcclusion = 1.0;
+
     // This is use with anisotropic material
     surfaceData.tangentWS = Orthonormalize(surfaceData.tangentWS, surfaceData.normalWS);
 
     // Use bent normal to sample GI if available
     // If any layer use a bent normal map, then bentNormalTS contain the interpolated result of bentnormal and normalmap (in case no bent normal are available)
     // Note: the code in LitDataInternal ensure that we fallback on normal map for layer that have no bentnormal
-    surfaceData.specularOcclusion = 1.0;
-    #ifdef _ENABLESPECULAROCCLUSION
-    // If we have bent normal and ambient occlusion, process a specular occlusion
-    surfaceData.specularOcclusion = GetSpecularOcclusionFromBentAO(V, bentNormalWS, surfaceData);
-    #endif
+#endif
+
+    // By default we use the ambient occlusion with Tri-ace trick (apply outside) for specular occlusion.
+    // If user provide bent normal then we process a better term
+#if (defined(_BENTNORMALMAP0) || defined(_BENTNORMALMAP1) || defined(_BENTNORMALMAP2) || defined(_BENTNORMALMAP3)) && defined(_ENABLESPECULAROCCLUSION)
+    // If we have bent normal and ambient occlusion, process a specular occlusion
+    surfaceData.specularOcclusion = GetSpecularOcclusionFromBentAO(V, bentNormalWS, surfaceData);
+#elif defined(_MASKMAP0) || defined(_MASKMAP1) || defined(_MASKMAP2) || defined(_MASKMAP3)
+    surfaceData.specularOcclusion = GetSpecularOcclusionFromAmbientOcclusion(dot(surfaceData.normalWS, V), surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
+#else
+    surfaceData.specularOcclusion = 1.0;
 #endif
 
     GetBuiltinData(input, surfaceData, alpha, bentNormalWS, depthOffset, builtinData);