From 1f7270f889ee0859d5257a3606c604073aa0cdb9 Mon Sep 17 00:00:00 2001
From: Adrien de Tocqueville <adrien.tocqueville@unity3d.com>
Date: Tue, 27 Jul 2021 16:02:24 +0200
Subject: [PATCH 1/7] Add two methods for specular occlusion based on spherical
 gaussians

---
 .../ShaderLibrary/CommonLighting.hlsl         | 69 ++++++++++++++++++-
 .../Editor/Material/Lit/LitGUI.cs             |  2 +
 .../Runtime/Material/Lit/Lit.shader           |  4 +-
 .../Runtime/Material/Lit/LitData.hlsl         | 15 ++--
 .../Runtime/Material/Lit/LitProperties.hlsl   |  2 +
 5 files changed, 81 insertions(+), 11 deletions(-)

diff --git a/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl b/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl
index 05617ac44f4..e571d96b324 100644
--- a/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl
+++ b/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl
@@ -245,7 +245,7 @@ real3 GTAOMultiBounce(real visibility, real3 albedo)
     return max(x, ((x * a + b) * x + c) * x);
 }
 
-// Based on Oat and Sander's 2008 technique
+// Based on Oat and Sander's 2007 technique
 // Area/solidAngle of intersection of two cone
 real SphericalCapIntersectionSolidArea(real cosC1, real cosC2, real cosB)
 {
@@ -290,6 +290,73 @@ real GetSpecularOcclusionFromBentAO(real3 V, real3 bentNormalWS, real3 normalWS,
     return SphericalCapIntersectionSolidArea(cosAv, cosAs, cosB) / (TWO_PI * (1.0 - cosAs));
 }
 
+float Square(float x)
+{
+    return x * x;
+}
+
+real GetSpecularOcclusionFromBentAO_ASG(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
+{
+    //AnisotropicSphericalGaussian NDF = WarpedGGXDistributionASG(normalWS, roughness, V);
+    //SphericalGaussian Visibility = VisibilityConeSG(bentNormalWS, ambientOcclusion);
+    //SphericalGaussian UpperHemisphere = UpperHemisphereSG(normalWS);
+    //return saturate( InnerProduct(NDF, Visibility) / InnerProduct(NDF, UpperHemisphere) );
+
+    // Approximation of the operation above:
+
+    // 1. Approximate visibility cone with a spherical gaussian of amplitude A=1
+    // For a cone angle X, we can determine sharpness so that all point inside the cone have a value > Y
+    // sharpness = (log(Y) - log(A)) / (cos(X) - 1)
+    // For AO cone, cos(X) = sqrt(1 - ambientOcclusion)
+    // -> for Y = 0.1, sharpness = -1.0 / (sqrt(1-ao) - 1)
+
+    const float nu1 = -0.5f / (sqrt(1.0f - ambientOcclusion) - 1.0f);
+
+    // 2. Approximate upper hemisphere with sharpness = 0.8 and amplitude = 1
+    const float nu2 = 0.5f * 0.8f;
+
+    // 3. Compute warped Anisotropic SG of GGX distribution
+    // Ref: http://cg.cs.tsinghua.edu.cn/people/~kun/asg/paper_asg.pdf
+    // https://therealmjp.github.io/posts/sg-series-part-4-specular-lighting-from-an-sg-light-source/#going-anisotropic
+    // use same sharpness for X and Y because it simplifies a lot and it doesn't change much
+    float NoV = dot(V, normalWS);
+    float3 R = 2 * NoV * normalWS - V;
+    float NDFSharpnessInv = 4.0f * roughness * roughness * NoV;
+    float3 NDFAxisX = cross(V, normalWS);
+    float3 NDFAxisY = cross(R, NDFAxisX);
+
+    //float amplitude = sqrt( ((nu1 + NDF.SharpnessX) * (nu1 + NDF.SharpnessY)) / ((nu2 + NDF.SharpnessX) * (nu2 + NDF.SharpnessY)) );
+    float amplitude = nu1 * NDFSharpnessInv + 1;    // Assuming sharpnessX == sharpnessY and nu2 << sharpness
+    float sharpness = nu1 / max(amplitude, 0.001f); // == (nu1 * NDF.SharpnessX) / (nu1 + NDF.SharpnessX);
+
+    // Ignore L2 cause it's mostly 0
+    float NDFAxisYNorm = 1.0f / dot(NDFAxisY, NDFAxisY);
+    float u1 = Square(dot(NDFAxisY, bentNormalWS)) * NDFAxisYNorm;
+    float u2 = Square(dot(NDFAxisY, normalWS))     * NDFAxisYNorm;
+    float L1 = Square(dot(NDFAxisX, bentNormalWS)) / dot(NDFAxisX, NDFAxisX);
+    float expFactor = exp(nu2 * u2 - sharpness * (L1 + u1));
+
+    // put expFactor 2 times because it looks nicer
+    return saturate(amplitude * expFactor * expFactor);
+}
+
+real GetSpecularOcclusionFromBentAO_SG(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
+{
+    // Same as GetSpecularOcclusionFromBentAO_ASG but with non anisotropic SG for GGX 
+    float us = 0.81f;
+    float vs = 1.0f / (sqrt(1.0f - ambientOcclusion) - 1.0f);
+    float3 NDFAxis = reflect(-V, normalWS) * (0.5f / max(roughness * roughness * dot(normalWS, V), 0.001));
+
+    float umLength1 = length(NDFAxis - vs * bentNormalWS);
+    float umLength2 = length(NDFAxis + us * normalWS);
+    float d1 = 1 - exp(-2 * umLength1);
+    float d2 = 1 - exp(-2 * umLength2);
+
+    float expFactor1 = exp(umLength1 - umLength2 + us + vs);
+
+    return saturate(expFactor1 * (d1 * umLength2) / (d2 * umLength1));
+}
+
 // Ref: Steve McAuley - Energy-Conserving Wrapped Diffuse
 real ComputeWrappedDiffuseLighting(real NdotL, real w)
 {
diff --git a/com.unity.render-pipelines.high-definition/Editor/Material/Lit/LitGUI.cs b/com.unity.render-pipelines.high-definition/Editor/Material/Lit/LitGUI.cs
index 83983ad1c2b..e448d5345cc 100644
--- a/com.unity.render-pipelines.high-definition/Editor/Material/Lit/LitGUI.cs
+++ b/com.unity.render-pipelines.high-definition/Editor/Material/Lit/LitGUI.cs
@@ -130,6 +130,8 @@ static public void SetupLitKeywordsAndPass(Material material)
                 int specOcclusionMode = material.GetInt(kSpecularOcclusionMode);
                 CoreUtils.SetKeyword(material, "_SPECULAR_OCCLUSION_NONE", specOcclusionMode == 0);
                 CoreUtils.SetKeyword(material, "_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP", specOcclusionMode == 2);
+                CoreUtils.SetKeyword(material, "_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG", specOcclusionMode == 3);
+                CoreUtils.SetKeyword(material, "_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG", specOcclusionMode == 4);
             }
             if (material.HasProperty(kHeightMap))
                 CoreUtils.SetKeyword(material, "_HEIGHTMAP", material.GetTexture(kHeightMap));
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader
index 7d72c2a71dc..615c393908e 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader
@@ -77,7 +77,7 @@ Shader "HDRP/Lit"
 
         // Following options are for the GUI inspector and different from the input parameters above
         // These option below will cause different compilation flag.
-        [Enum(Off, 0, From Ambient Occlusion, 1, From Bent Normals, 2)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
+        [Enum(Off, 0, From Ambient Occlusion, 1, From Bent Normals, 2, From Spherical Gaussians, 3, From Anisotropic Spherical Gaussians, 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
 
         [HDR] _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         // Used only to serialize the LDR and HDR emissive color in the material UI,
@@ -257,7 +257,7 @@ Shader "HDRP/Lit"
     // _ENABLESPECULAROCCLUSION and _SPECULAR_OCCLUSION_X can't exist at the same time (the new _SPECULAR_OCCLUSION replace it)
     // When _ENABLESPECULAROCCLUSION is found we define _SPECULAR_OCCLUSION_X so new code to work
     #pragma shader_feature_local_fragment _ENABLESPECULAROCCLUSION
-    #pragma shader_feature_local_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
+    #pragma shader_feature_local_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG
     #pragma shader_feature_local_raytracing _ENABLESPECULAROCCLUSION
     #pragma shader_feature_local_raytracing _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
 
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitData.hlsl b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitData.hlsl
index 31cef50350c..397b1f5ec7e 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitData.hlsl
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitData.hlsl
@@ -17,9 +17,6 @@
 #include "Packages/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitDecalData.hlsl"
 #endif
 
-//#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Material/SphericalCapPivot/SPTDistribution.hlsl"
-//#define SPECULAR_OCCLUSION_USE_SPTD
-
 //#define PROJECTED_SPACE_NDF_FILTERING
 
 // Struct that gather UVMapping info of all layers + common calculation
@@ -284,13 +281,15 @@ void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs p
 
     // 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(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP)
+#if defined(_BENTNORMALMAP) && (defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP) || defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG) || defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG))
     // If we have bent normal and ambient occlusion, process a specular occlusion
-    #ifdef SPECULAR_OCCLUSION_USE_SPTD
-    surfaceData.specularOcclusion = GetSpecularOcclusionFromBentAOPivot(V, bentNormalWS, surfaceData.normalWS, surfaceData.ambientOcclusion, PerceptualSmoothnessToPerceptualRoughness(surfaceData.perceptualSmoothness));
-    #else
+    #ifdef _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
     surfaceData.specularOcclusion = GetSpecularOcclusionFromBentAO(V, bentNormalWS, surfaceData.normalWS, surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
-#endif
+    #elif defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG)
+    surfaceData.specularOcclusion = GetSpecularOcclusionFromBentAO_SG(V, bentNormalWS, surfaceData.normalWS, surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
+    #elif defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG)
+    surfaceData.specularOcclusion = GetSpecularOcclusionFromBentAO_ASG(V, bentNormalWS, surfaceData.normalWS, surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
+    #endif
     // Don't do spec occ from Ambient if there is no mask mask
 #elif defined(_MASKMAP) && !defined(_SPECULAR_OCCLUSION_NONE)
     surfaceData.specularOcclusion = GetSpecularOcclusionFromAmbientOcclusion(ClampNdotV(dot(surfaceData.normalWS, V)), surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitProperties.hlsl b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitProperties.hlsl
index d20882376c4..9eed7799baf 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitProperties.hlsl
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitProperties.hlsl
@@ -22,6 +22,8 @@ TEXTURE2D(_MaskMap);
 SAMPLER(sampler_MaskMap);
 TEXTURE2D(_BentNormalMap); // Reuse sampler from normal map
 SAMPLER(sampler_BentNormalMap);
+TEXTURE2D(_BentNormalMapOS);
+SAMPLER(sampler_BentNormalMapOS);
 
 TEXTURE2D(_NormalMap);
 SAMPLER(sampler_NormalMap);

From 2bbce333412a5009401f4040bef21f8227bc384e Mon Sep 17 00:00:00 2001
From: Adrien de Tocqueville <adrien.tocqueville@unity3d.com>
Date: Thu, 5 Aug 2021 20:35:54 +0200
Subject: [PATCH 2/7] Add to all lit shaders

---
 .../Runtime/Material/LayeredLit/LayeredLit.shader             | 4 ++--
 .../Runtime/Material/LayeredLit/LayeredLitTessellation.shader | 4 ++--
 .../Runtime/Material/Lit/Lit.shader                           | 2 +-
 .../Runtime/Material/Lit/LitTessellation.shader               | 4 ++--
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLit.shader b/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLit.shader
index b54c1e7aa98..71f339499f8 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLit.shader
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLit.shader
@@ -244,7 +244,7 @@ Shader "HDRP/LayeredLit"
 
         // Following are builtin properties
 
-        [Enum(Off, 0, From Ambient Occlusion, 1, From Bent Normals, 2)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
+        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2, From AO and Bent Normals (SG), 3, From AO and Bent Normals (ASG), 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
 
         [HDR] _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         // Used only to serialize the LDR and HDR emissive color in the material UI,
@@ -451,7 +451,7 @@ Shader "HDRP/LayeredLit"
     // _ENABLESPECULAROCCLUSION and _SPECULAR_OCCLUSION_X can't exist at the same time (the new _SPECULAR_OCCLUSION replace it)
     // When _ENABLESPECULAROCCLUSION is found we define _SPECULAR_OCCLUSION_X so new code to work
     #pragma shader_feature_fragment _ENABLESPECULAROCCLUSION                     // Non-local
-    #pragma shader_feature_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP // Non-local
+    #pragma shader_feature_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG // Non-local
     #pragma shader_feature_raytracing _ENABLESPECULAROCCLUSION                     // Non-local
     #pragma shader_feature_raytracing _ SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP // Non-local
 
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitTessellation.shader b/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitTessellation.shader
index a9c9fa29f9b..4b2c8501a08 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitTessellation.shader
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitTessellation.shader
@@ -244,7 +244,7 @@ Shader "HDRP/LayeredLitTessellation"
 
         // Following are builtin properties
 
-        [Enum(Off, 0, From Ambient Occlusion, 1, From Bent Normals, 2)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
+        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2, From AO and Bent Normals (SG), 3, From AO and Bent Normals (ASG), 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
 
         [HDR] _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         // Used only to serialize the LDR and HDR emissive color in the material UI,
@@ -461,7 +461,7 @@ Shader "HDRP/LayeredLitTessellation"
     // _ENABLESPECULAROCCLUSION and _SPECULAR_OCCLUSION_X can't exist at the same time (the new _SPECULAR_OCCLUSION replace it)
     // When _ENABLESPECULAROCCLUSION is found we define _SPECULAR_OCCLUSION_X so new code to work
     #pragma shader_feature _ENABLESPECULAROCCLUSION                     // Non-local
-    #pragma shader_feature _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP // Non-local
+    #pragma shader_feature_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG // Non-local
     #ifdef _ENABLESPECULAROCCLUSION
     #define _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
     #endif
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader
index 615c393908e..96a4800908a 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader
@@ -77,7 +77,7 @@ Shader "HDRP/Lit"
 
         // Following options are for the GUI inspector and different from the input parameters above
         // These option below will cause different compilation flag.
-        [Enum(Off, 0, From Ambient Occlusion, 1, From Bent Normals, 2, From Spherical Gaussians, 3, From Anisotropic Spherical Gaussians, 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
+        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2, From AO and Bent Normals (SG), 3, From AO and Bent Normals (ASG), 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
 
         [HDR] _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         // Used only to serialize the LDR and HDR emissive color in the material UI,
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitTessellation.shader b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitTessellation.shader
index 3da0a6e2762..cc3eaed5586 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitTessellation.shader
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitTessellation.shader
@@ -77,7 +77,7 @@ Shader "HDRP/LitTessellation"
 
         // Following options are for the GUI inspector and different from the input parameters above
         // These option below will cause different compilation flag.
-        [Enum(Off, 0, From Ambient Occlusion, 1, From Bent Normals, 2)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
+        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2, From AO and Bent Normals (SG), 3, From AO and Bent Normals (ASG), 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
 
         [HDR] _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         // Used only to serialize the LDR and HDR emissive color in the material UI,
@@ -268,7 +268,7 @@ Shader "HDRP/LitTessellation"
     // _ENABLESPECULAROCCLUSION and _SPECULAR_OCCLUSION_X can't exist at the same time (the new _SPECULAR_OCCLUSION replace it)
     // When _ENABLESPECULAROCCLUSION is found we define _SPECULAR_OCCLUSION_X so new code to work
     #pragma shader_feature_local_fragment _ENABLESPECULAROCCLUSION
-    #pragma shader_feature_local_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
+    #pragma shader_feature_local_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG
     #pragma shader_feature_local_raytracing _ENABLESPECULAROCCLUSION
     #pragma shader_feature_local_raytracing _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
 

From c42c4e32b3bbe3906046f9d0cdc1ac25314c1d0d Mon Sep 17 00:00:00 2001
From: Adrien de Tocqueville <adrien.tocqueville@unity3d.com>
Date: Tue, 31 Aug 2021 18:09:02 +0200
Subject: [PATCH 3/7] Set SG version as default

---
 .../ShaderLibrary/CommonLighting.hlsl         | 54 ++++---------------
 .../CHANGELOG.md                              |  1 +
 .../Editor/Material/Lit/LitGUI.cs             |  2 -
 .../ShaderGraph/TargetData/LightingData.cs    |  2 +-
 .../Material/LayeredLit/LayeredLit.shader     |  6 +--
 .../LayeredLit/LayeredLitTessellation.shader  |  4 +-
 .../Runtime/Material/Lit/Lit.shader           |  4 +-
 .../Runtime/Material/Lit/LitData.hlsl         |  8 +--
 .../Material/Lit/LitTessellation.shader       |  4 +-
 9 files changed, 23 insertions(+), 62 deletions(-)

diff --git a/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl b/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl
index e571d96b324..504ff0e1fc3 100644
--- a/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl
+++ b/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl
@@ -279,7 +279,7 @@ real SphericalCapIntersectionSolidArea(real cosC1, real cosC2, real cosB)
 // ref: Practical Realtime Strategies for Accurate Indirect Occlusion
 // http://blog.selfshadow.com/publications/s2016-shading-course/#course_content
 // Original Cone-Cone method with cosine weighted assumption (p129 s2016_pbs_activision_occlusion)
-real GetSpecularOcclusionFromBentAO(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
+real GetSpecularOcclusionFromBentAO_ConeCone(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
 {
     // Retrieve cone angle
     // Ambient occlusion is cosine weighted, thus use following equation. See slide 129
@@ -290,14 +290,9 @@ real GetSpecularOcclusionFromBentAO(real3 V, real3 bentNormalWS, real3 normalWS,
     return SphericalCapIntersectionSolidArea(cosAv, cosAs, cosB) / (TWO_PI * (1.0 - cosAs));
 }
 
-float Square(float x)
-{
-    return x * x;
-}
-
-real GetSpecularOcclusionFromBentAO_ASG(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
+real GetSpecularOcclusionFromBentAO(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
 {
-    //AnisotropicSphericalGaussian NDF = WarpedGGXDistributionASG(normalWS, roughness, V);
+    //SphericalGaussian NDF = WarpedGGXDistribution(normalWS, roughness, V);
     //SphericalGaussian Visibility = VisibilityConeSG(bentNormalWS, ambientOcclusion);
     //SphericalGaussian UpperHemisphere = UpperHemisphereSG(normalWS);
     //return saturate( InnerProduct(NDF, Visibility) / InnerProduct(NDF, UpperHemisphere) );
@@ -309,50 +304,23 @@ real GetSpecularOcclusionFromBentAO_ASG(real3 V, real3 bentNormalWS, real3 norma
     // sharpness = (log(Y) - log(A)) / (cos(X) - 1)
     // For AO cone, cos(X) = sqrt(1 - ambientOcclusion)
     // -> for Y = 0.1, sharpness = -1.0 / (sqrt(1-ao) - 1)
-
-    const float nu1 = -0.5f / (sqrt(1.0f - ambientOcclusion) - 1.0f);
+    float vs = -1.0f / (sqrt(1.0f - ambientOcclusion) - 1.0f);
 
     // 2. Approximate upper hemisphere with sharpness = 0.8 and amplitude = 1
-    const float nu2 = 0.5f * 0.8f;
+    float us = 0.8f;
 
-    // 3. Compute warped Anisotropic SG of GGX distribution
-    // Ref: http://cg.cs.tsinghua.edu.cn/people/~kun/asg/paper_asg.pdf
-    // https://therealmjp.github.io/posts/sg-series-part-4-specular-lighting-from-an-sg-light-source/#going-anisotropic
-    // use same sharpness for X and Y because it simplifies a lot and it doesn't change much
+    // 3. Compute warped SG Axis of GGX distribution
+    // Ref: All-Frequency Rendering of Dynamic, Spatially-Varying Reflectance
+    // https://www.microsoft.com/en-us/research/wp-content/uploads/2009/12/sg.pdf
     float NoV = dot(V, normalWS);
-    float3 R = 2 * NoV * normalWS - V;
-    float NDFSharpnessInv = 4.0f * roughness * roughness * NoV;
-    float3 NDFAxisX = cross(V, normalWS);
-    float3 NDFAxisY = cross(R, NDFAxisX);
-
-    //float amplitude = sqrt( ((nu1 + NDF.SharpnessX) * (nu1 + NDF.SharpnessY)) / ((nu2 + NDF.SharpnessX) * (nu2 + NDF.SharpnessY)) );
-    float amplitude = nu1 * NDFSharpnessInv + 1;    // Assuming sharpnessX == sharpnessY and nu2 << sharpness
-    float sharpness = nu1 / max(amplitude, 0.001f); // == (nu1 * NDF.SharpnessX) / (nu1 + NDF.SharpnessX);
-
-    // Ignore L2 cause it's mostly 0
-    float NDFAxisYNorm = 1.0f / dot(NDFAxisY, NDFAxisY);
-    float u1 = Square(dot(NDFAxisY, bentNormalWS)) * NDFAxisYNorm;
-    float u2 = Square(dot(NDFAxisY, normalWS))     * NDFAxisYNorm;
-    float L1 = Square(dot(NDFAxisX, bentNormalWS)) / dot(NDFAxisX, NDFAxisX);
-    float expFactor = exp(nu2 * u2 - sharpness * (L1 + u1));
-
-    // put expFactor 2 times because it looks nicer
-    return saturate(amplitude * expFactor * expFactor);
-}
-
-real GetSpecularOcclusionFromBentAO_SG(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
-{
-    // Same as GetSpecularOcclusionFromBentAO_ASG but with non anisotropic SG for GGX 
-    float us = 0.81f;
-    float vs = 1.0f / (sqrt(1.0f - ambientOcclusion) - 1.0f);
-    float3 NDFAxis = reflect(-V, normalWS) * (0.5f / max(roughness * roughness * dot(normalWS, V), 0.001));
+    float3 NDFAxis = (2 * NoV * normalWS - V) * (0.5f / max(roughness * roughness * NoV, 0.001f));
 
-    float umLength1 = length(NDFAxis - vs * bentNormalWS);
+    float umLength1 = length(NDFAxis + vs * bentNormalWS);
     float umLength2 = length(NDFAxis + us * normalWS);
     float d1 = 1 - exp(-2 * umLength1);
     float d2 = 1 - exp(-2 * umLength2);
 
-    float expFactor1 = exp(umLength1 - umLength2 + us + vs);
+    float expFactor1 = exp(umLength1 - umLength2 + us - vs);
 
     return saturate(expFactor1 * (d1 * umLength2) / (d2 * umLength1));
 }
diff --git a/com.unity.render-pipelines.high-definition/CHANGELOG.md b/com.unity.render-pipelines.high-definition/CHANGELOG.md
index 2971190cdb1..d2ced209e23 100644
--- a/com.unity.render-pipelines.high-definition/CHANGELOG.md
+++ b/com.unity.render-pipelines.high-definition/CHANGELOG.md
@@ -378,6 +378,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed case where the SceneView don't refresh when using LightExplorer with a running and Paused game (1354129)
 - Fixed wrong ordering in FrameSettings (Normalize Reflection Probes)
 - Allow negative wind speed parameter.
+- Fixed specular occlusion sharpness and over darkening at grazing angles.
 
 ### Changed
 - Changed Window/Render Pipeline/HD Render Pipeline Wizard to Window/Rendering/HDRP Wizard
diff --git a/com.unity.render-pipelines.high-definition/Editor/Material/Lit/LitGUI.cs b/com.unity.render-pipelines.high-definition/Editor/Material/Lit/LitGUI.cs
index e448d5345cc..83983ad1c2b 100644
--- a/com.unity.render-pipelines.high-definition/Editor/Material/Lit/LitGUI.cs
+++ b/com.unity.render-pipelines.high-definition/Editor/Material/Lit/LitGUI.cs
@@ -130,8 +130,6 @@ static public void SetupLitKeywordsAndPass(Material material)
                 int specOcclusionMode = material.GetInt(kSpecularOcclusionMode);
                 CoreUtils.SetKeyword(material, "_SPECULAR_OCCLUSION_NONE", specOcclusionMode == 0);
                 CoreUtils.SetKeyword(material, "_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP", specOcclusionMode == 2);
-                CoreUtils.SetKeyword(material, "_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG", specOcclusionMode == 3);
-                CoreUtils.SetKeyword(material, "_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG", specOcclusionMode == 4);
             }
             if (material.HasProperty(kHeightMap))
                 CoreUtils.SetKeyword(material, "_HEIGHTMAP", material.GetTexture(kHeightMap));
diff --git a/com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/TargetData/LightingData.cs b/com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/TargetData/LightingData.cs
index cd4b56e5a72..0a3878e4caf 100644
--- a/com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/TargetData/LightingData.cs
+++ b/com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/TargetData/LightingData.cs
@@ -74,7 +74,7 @@ public bool specularAA
         // }
 
         [SerializeField]
-        SpecularOcclusionMode m_SpecularOcclusionMode;
+        SpecularOcclusionMode m_SpecularOcclusionMode = SpecularOcclusionMode.FromAO;
         public SpecularOcclusionMode specularOcclusionMode
         {
             get => m_SpecularOcclusionMode;
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLit.shader b/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLit.shader
index 6ae2f8463e2..a28294fda2b 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLit.shader
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLit.shader
@@ -244,7 +244,7 @@ Shader "HDRP/LayeredLit"
 
         // Following are builtin properties
 
-        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2, From AO and Bent Normals (SG), 3, From AO and Bent Normals (ASG), 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
+        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
 
         [HDR] _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         // Used only to serialize the LDR and HDR emissive color in the material UI,
@@ -451,9 +451,9 @@ Shader "HDRP/LayeredLit"
     // _ENABLESPECULAROCCLUSION and _SPECULAR_OCCLUSION_X can't exist at the same time (the new _SPECULAR_OCCLUSION replace it)
     // When _ENABLESPECULAROCCLUSION is found we define _SPECULAR_OCCLUSION_X so new code to work
     #pragma shader_feature_fragment _ENABLESPECULAROCCLUSION                     // Non-local
-    #pragma shader_feature_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG // Non-local
+    #pragma shader_feature_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP // Non-local
     #pragma shader_feature_raytracing _ENABLESPECULAROCCLUSION                     // Non-local
-    #pragma shader_feature_raytracing _ SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP // Non-local
+    #pragma shader_feature_raytracing _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP // Non-local
 
     #ifdef _ENABLESPECULAROCCLUSION
     #define _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitTessellation.shader b/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitTessellation.shader
index f936751854a..d79b23c3be1 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitTessellation.shader
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitTessellation.shader
@@ -244,7 +244,7 @@ Shader "HDRP/LayeredLitTessellation"
 
         // Following are builtin properties
 
-        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2, From AO and Bent Normals (SG), 3, From AO and Bent Normals (ASG), 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
+        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
 
         [HDR] _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         // Used only to serialize the LDR and HDR emissive color in the material UI,
@@ -461,7 +461,7 @@ Shader "HDRP/LayeredLitTessellation"
     // _ENABLESPECULAROCCLUSION and _SPECULAR_OCCLUSION_X can't exist at the same time (the new _SPECULAR_OCCLUSION replace it)
     // When _ENABLESPECULAROCCLUSION is found we define _SPECULAR_OCCLUSION_X so new code to work
     #pragma shader_feature _ENABLESPECULAROCCLUSION                     // Non-local
-    #pragma shader_feature_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG // Non-local
+    #pragma shader_feature _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP // Non-local
     #ifdef _ENABLESPECULAROCCLUSION
     #define _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
     #endif
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader
index 82f7fc719ea..5501967ffcf 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.shader
@@ -77,7 +77,7 @@ Shader "HDRP/Lit"
 
         // Following options are for the GUI inspector and different from the input parameters above
         // These option below will cause different compilation flag.
-        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2, From AO and Bent Normals (SG), 3, From AO and Bent Normals (ASG), 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
+        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
 
         [HDR] _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         // Used only to serialize the LDR and HDR emissive color in the material UI,
@@ -257,7 +257,7 @@ Shader "HDRP/Lit"
     // _ENABLESPECULAROCCLUSION and _SPECULAR_OCCLUSION_X can't exist at the same time (the new _SPECULAR_OCCLUSION replace it)
     // When _ENABLESPECULAROCCLUSION is found we define _SPECULAR_OCCLUSION_X so new code to work
     #pragma shader_feature_local_fragment _ENABLESPECULAROCCLUSION
-    #pragma shader_feature_local_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG
+    #pragma shader_feature_local_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
     #pragma shader_feature_local_raytracing _ENABLESPECULAROCCLUSION
     #pragma shader_feature_local_raytracing _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
 
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitData.hlsl b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitData.hlsl
index 397b1f5ec7e..729fa81e0b2 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitData.hlsl
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitData.hlsl
@@ -281,15 +281,9 @@ void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs p
 
     // 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(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP) || defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG) || defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG))
+#if defined(_BENTNORMALMAP) && defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP)
     // If we have bent normal and ambient occlusion, process a specular occlusion
-    #ifdef _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
     surfaceData.specularOcclusion = GetSpecularOcclusionFromBentAO(V, bentNormalWS, surfaceData.normalWS, surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
-    #elif defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG)
-    surfaceData.specularOcclusion = GetSpecularOcclusionFromBentAO_SG(V, bentNormalWS, surfaceData.normalWS, surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
-    #elif defined(_SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG)
-    surfaceData.specularOcclusion = GetSpecularOcclusionFromBentAO_ASG(V, bentNormalWS, surfaceData.normalWS, surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
-    #endif
     // Don't do spec occ from Ambient if there is no mask mask
 #elif defined(_MASKMAP) && !defined(_SPECULAR_OCCLUSION_NONE)
     surfaceData.specularOcclusion = GetSpecularOcclusionFromAmbientOcclusion(ClampNdotV(dot(surfaceData.normalWS, V)), surfaceData.ambientOcclusion, PerceptualSmoothnessToRoughness(surfaceData.perceptualSmoothness));
diff --git a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitTessellation.shader b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitTessellation.shader
index 4e2a5cf3ada..ce88d3f398f 100644
--- a/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitTessellation.shader
+++ b/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitTessellation.shader
@@ -77,7 +77,7 @@ Shader "HDRP/LitTessellation"
 
         // Following options are for the GUI inspector and different from the input parameters above
         // These option below will cause different compilation flag.
-        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2, From AO and Bent Normals (SG), 3, From AO and Bent Normals (ASG), 4)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
+        [Enum(Off, 0, From Ambient Occlusion, 1, From AO and Bent Normals, 2)]  _SpecularOcclusionMode("Specular Occlusion Mode", Int) = 1
 
         [HDR] _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         // Used only to serialize the LDR and HDR emissive color in the material UI,
@@ -268,7 +268,7 @@ Shader "HDRP/LitTessellation"
     // _ENABLESPECULAROCCLUSION and _SPECULAR_OCCLUSION_X can't exist at the same time (the new _SPECULAR_OCCLUSION replace it)
     // When _ENABLESPECULAROCCLUSION is found we define _SPECULAR_OCCLUSION_X so new code to work
     #pragma shader_feature_local_fragment _ENABLESPECULAROCCLUSION
-    #pragma shader_feature_local_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_SG _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP_ASG
+    #pragma shader_feature_local_fragment _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
     #pragma shader_feature_local_raytracing _ENABLESPECULAROCCLUSION
     #pragma shader_feature_local_raytracing _ _SPECULAR_OCCLUSION_NONE _SPECULAR_OCCLUSION_FROM_BENT_NORMAL_MAP
 

From 4fe1bb77f5ba372c35fe759cbb7b638f39edc530 Mon Sep 17 00:00:00 2001
From: Adrien de Tocqueville <adrien.tocqueville@unity3d.com>
Date: Wed, 1 Sep 2021 11:12:43 +0200
Subject: [PATCH 4/7] Update screenshots

---
 .../Linear/LinuxEditor/Vulkan/None/1210_Lit_BentNormal.png    | 4 ++--
 .../Linear/OSXEditor/Metal/None/1210_Lit_BentNormal.png       | 4 ++--
 .../WindowsEditor/Direct3D11/None/1210_Lit_BentNormal.png     | 4 ++--
 .../Linear/WindowsEditor/Vulkan/None/1210_Lit_BentNormal.png  | 4 ++--
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/LinuxEditor/Vulkan/None/1210_Lit_BentNormal.png b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/LinuxEditor/Vulkan/None/1210_Lit_BentNormal.png
index 51d7c1faaa8..427e89e5b72 100644
--- a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/LinuxEditor/Vulkan/None/1210_Lit_BentNormal.png
+++ b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/LinuxEditor/Vulkan/None/1210_Lit_BentNormal.png
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:bdaa894b3cd3a8a6ae48d3cfc20d2068920db6aefc00f40621149647cfc4a9ee
-size 174564
+oid sha256:ef77d89a884c94e69c0981c576f7538b8305e69ac0e6d3e33a548207f38ac82c
+size 153225
diff --git a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/OSXEditor/Metal/None/1210_Lit_BentNormal.png b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/OSXEditor/Metal/None/1210_Lit_BentNormal.png
index a4789b62f38..d5c04b086da 100644
--- a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/OSXEditor/Metal/None/1210_Lit_BentNormal.png
+++ b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/OSXEditor/Metal/None/1210_Lit_BentNormal.png
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:43d968134620179d1a0998174fe208aff8922959dad93d77538cdebb2fbc63db
-size 152713
+oid sha256:2a277bafebf1d50f506144f0c18a4448dd3eca2215cf092ba1eb61ff61ee7aff
+size 152947
diff --git a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D11/None/1210_Lit_BentNormal.png b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D11/None/1210_Lit_BentNormal.png
index 0bd6dcb3171..0802ee6697b 100644
--- a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D11/None/1210_Lit_BentNormal.png
+++ b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D11/None/1210_Lit_BentNormal.png
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:22a865a7db80ef101242ce4f23cf3d846ec542cac7422810ed7424a7351c7f7c
-size 153072
+oid sha256:255b0c7bb1445a57659c17f3d7bcc4a05bd5970f19aadaa6c73b0da7e9e83096
+size 153148
diff --git a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Vulkan/None/1210_Lit_BentNormal.png b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Vulkan/None/1210_Lit_BentNormal.png
index 8cb522aeaf4..427e89e5b72 100644
--- a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Vulkan/None/1210_Lit_BentNormal.png
+++ b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Vulkan/None/1210_Lit_BentNormal.png
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:7deb071c27433c51b50c915065817b466252555d2e3b9428593eb2acf3183e55
-size 152903
+oid sha256:ef77d89a884c94e69c0981c576f7538b8305e69ac0e6d3e33a548207f38ac82c
+size 153225

From 83b754678441dc98bcf3130688d29fcc7016a6a5 Mon Sep 17 00:00:00 2001
From: Adrien de Tocqueville <adrien.tocqueville@unity3d.com>
Date: Thu, 2 Sep 2021 13:23:32 +0200
Subject: [PATCH 5/7] dx12 screenshot test

---
 .../WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png     | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png
index 7e770153d4a..5a33a60d264 100644
--- a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png
+++ b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:638dbedea46a9b053d04bf35f5269631246ab215a606c091f2720e9a1f2867a8
-size 153160
+oid sha256:2d0d5bc5d1f072eafa1d031d45d37c420e92c716e6eb4e1164f48325a2c8b7ec
+size 138653

From ae41cc8fe95e66695092f4d4741047e74bb7432c Mon Sep 17 00:00:00 2001
From: Adrien de Tocqueville <adrien.tocqueville@unity3d.com>
Date: Thu, 2 Sep 2021 15:11:06 +0200
Subject: [PATCH 6/7] real screenshot

---
 .../WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png     | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png
index 5a33a60d264..6b320949612 100644
--- a/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png
+++ b/TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Direct3D12/None/1210_Lit_BentNormal.png
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:2d0d5bc5d1f072eafa1d031d45d37c420e92c716e6eb4e1164f48325a2c8b7ec
-size 138653
+oid sha256:f60718ffd796662561b9ac0a3d48fa55d3943b09c2ca942e420c6ece8882e9b7
+size 153158

From 207a5a30647e468e0d6a0c590af8422160a819b7 Mon Sep 17 00:00:00 2001
From: Adrien de Tocqueville <adrien.tocqueville@unity3d.com>
Date: Fri, 3 Sep 2021 14:35:01 +0200
Subject: [PATCH 7/7] review

---
 .../ShaderLibrary/CommonLighting.hlsl                        | 3 +--
 .../Documentation~/Upgrading-from-2021.1-to-2021.2.md        | 5 +++++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl b/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl
index 504ff0e1fc3..c9dbf658d2f 100644
--- a/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl
+++ b/com.unity.render-pipelines.core/ShaderLibrary/CommonLighting.hlsl
@@ -292,13 +292,12 @@ real GetSpecularOcclusionFromBentAO_ConeCone(real3 V, real3 bentNormalWS, real3
 
 real GetSpecularOcclusionFromBentAO(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
 {
+    // Pseudo code:
     //SphericalGaussian NDF = WarpedGGXDistribution(normalWS, roughness, V);
     //SphericalGaussian Visibility = VisibilityConeSG(bentNormalWS, ambientOcclusion);
     //SphericalGaussian UpperHemisphere = UpperHemisphereSG(normalWS);
     //return saturate( InnerProduct(NDF, Visibility) / InnerProduct(NDF, UpperHemisphere) );
 
-    // Approximation of the operation above:
-
     // 1. Approximate visibility cone with a spherical gaussian of amplitude A=1
     // For a cone angle X, we can determine sharpness so that all point inside the cone have a value > Y
     // sharpness = (log(Y) - log(A)) / (cos(X) - 1)
diff --git a/com.unity.render-pipelines.high-definition/Documentation~/Upgrading-from-2021.1-to-2021.2.md b/com.unity.render-pipelines.high-definition/Documentation~/Upgrading-from-2021.1-to-2021.2.md
index e40182b802d..0fa05b8584e 100644
--- a/com.unity.render-pipelines.high-definition/Documentation~/Upgrading-from-2021.1-to-2021.2.md
+++ b/com.unity.render-pipelines.high-definition/Documentation~/Upgrading-from-2021.1-to-2021.2.md
@@ -39,6 +39,11 @@ HDRP 2021.2 has various tessellation shader code to enable tessellation support
 * HDRP has improved support of motion vectors for tessellation. Only `previousPositionRWS` is part of the varyings. HDRP also added the `MotionVectorTessellation()` function. For more information, see the `MotionVectorVertexShaderCommon.hlsl` file.
 * HDRP now evaluates the `tessellationFactor` in the vertex shader and passes it to the hull shader as an interpolator. For more information, see the `VaryingMesh.hlsl` and `VertMesh.hlsl` files.
 
+### Specular Occlusion
+
+The algorithm for computing specular occlusion from bent normals and ambient occlusion has been changed to improve visual results.
+To use the old algorithm, function calls to `GetSpecularOcclusionFromBentAO` should be replaced by calls to `GetSpecularOcclusionFromBentAO_ConeCone`
+
 ## Density Volumes
 
 Density Volumes are now known as **Local Volumetric Fog**.