Add support of Texture filtering (seems to not work yet)

com.unity.render-pipelines.core/CoreRP/ShaderLibrary/CommonMaterial.hlsl

     return sqrt(2.0 / (variance + 2.0));
 }
 
-float FilterPerceptualSmoothness(float perceptualSmoothness, float variance, float threshold)
+// Return modified perceptualSmoothness based on provided variance (get from GeometricNormalVariance + TextureNormalVariance)
+float NormalFiltering(float perceptualSmoothness, float variance, float threshold)
 {
     float roughness = PerceptualSmoothnessToRoughness(perceptualSmoothness);
     // Ref: Geometry into Shading - http://graphics.pixar.com/library/BumpRoughness/paper.pdf - equation (3)
 // This is the deferred approximation, which works reasonably well so we keep it for forward too for now.
 // screenSpaceVariance should be at most 0.5^2 = 0.25, as that corresponds to considering
 // a gaussian pixel reconstruction kernel with a standard deviation of 0.5 of a pixel, thus 2 sigma covering the whole pixel.
-float GeometricFilterVariance(float3 geometricNormalWS, float screenSpaceVariance)
+float GeometricNormalVariance(float3 geometricNormalWS, float screenSpaceVariance)
 {
     float3 deltaU = ddx(geometricNormalWS);
     float3 deltaV = ddy(geometricNormalWS);
 
-float GeometricFilterPerceptualSmoothness(float perceptualSmoothness, float3 geometricNormalWS, float screenSpaceVariance, float threshold)
+// Return modified perceptualSmoothness
+float GeometricNormalFiltering(float perceptualSmoothness, float3 geometricNormalWS, float screenSpaceVariance, float threshold)
-    float variance = GeometricFilterVariance(geometricNormalWS, screenSpaceVariance);
-    return FilterPerceptualSmoothness(perceptualSmoothness, variance, threshold);
+    float variance = GeometricNormalVariance(geometricNormalWS, screenSpaceVariance);
+    return NormalFiltering(perceptualSmoothness, variance, threshold);
 }
 
 // Normal map filtering based on The Order : 1886 SIGGRAPH course notes implementation.
 // Note that hw filtering on the normal map should be trilinear to be conservative, while anisotropic 
 // risk underfiltering. Could also compute average normal on the fly with a proper normal map format,
 // like Toksvig.
-float TextureFilteringVariance(float avgNormalLength)
+float TextureNormalVariance(float avgNormalLength)
 {
     if (avgNormalLength < 1.0)
     {
         return 0.25 * kappa;
     }
 
-    return 0.0f;
+    return 0.0;
-float TextureFilterPerceptualSmoothness(float perceptualSmoothness, float avgNormalLength, float threshold)
+float TextureNormalFiltering(float perceptualSmoothness, float avgNormalLength, float threshold)
-    float variance = TextureFilteringVariance(avgNormalLength);
-    return FilterPerceptualSmoothness(perceptualSmoothness, variance, threshold);
+    float variance = TextureNormalVariance(avgNormalLength);
+    return NormalFiltering(perceptualSmoothness, variance, threshold);
 }
 
 // ----------------------------------------------------------------------------

com.unity.render-pipelines.high-definition/HDRP/Editor/AssetPostProcessors/NormalMapVarianceTexturePostprocessor.cs

 using UnityEditor;
 using UnityEngine;
 
-public class NormalMapVarianceTexturePostprocessor : AssetPostprocessor
+public class NormalMapAverageLengthTexturePostprocessor : AssetPostprocessor
-    static string s_Extension = "_NA";
+    // This class will process a normal map and add the value of average normal length to the blue or alpha channel
+    // The texture is save as BC7.
+    // Tangent space normal map: BC7 RGB (normal xy - average normal length)
+    // Object space normal map: BC7 RGBA (normal xyz - average normal length)
+    static string s_Suffix = "_NA";
+    //static string s_SuffixOS = "_OSNA"; // Suffix for object space case - TODO
+
-        if (assetPath.IndexOf("_NA", StringComparison.InvariantCultureIgnoreCase) != -1)
+        if (assetPath.IndexOf(s_Suffix, StringComparison.InvariantCultureIgnoreCase) != -1)
-            textureImporter.textureCompression = TextureImporterCompression.CompressedHQ;
+            textureImporter.alphaSource = TextureImporterAlphaSource.None;
+            textureImporter.mipmapEnabled = true;
+            textureImporter.textureCompression = TextureImporterCompression.CompressedHQ; // This is BC7 for Mac/PC
 
 #pragma warning disable 618 // remove obsolete warning for this one
             textureImporter.linearTexture = true; // Says deprecated but won't work without it.
 
     void OnPostprocessTexture(Texture2D texture)
     {
-        if (assetPath.IndexOf("_NA", StringComparison.InvariantCultureIgnoreCase) != -1)
+        if (assetPath.IndexOf(s_Suffix, StringComparison.InvariantCultureIgnoreCase) != -1)
-            // For mip 0, set the normal length to 1.
-            {
-                Color[] c = texture.GetPixels(0);
-                for (int i = 0; i < c.Length; i++)
-                {
-                    c[i].a = 1.0f;
-                }
-                texture.SetPixels(c, 0);
-            }
-
             // Based on The Order : 1886 SIGGRAPH course notes implementation. Sample all normal map
             // texels from the base mip level that are within the footprint of the current mipmap texel.
             Color[] source = texture.GetPixels(0);
 
                         // Store the normal length for the average normal.
                         int outputPosition = y * mipWidth + x;
-                        //c[outputPosition].a = averageNormal.magnitude;
+
+                        // Clamp to avoid any issue (TODO: Check this)
+                        // Write into the blue channel
+                        float averageNormalLength = Math.Max(0.0f, Math.Min(1.0f, averageNormal.magnitude));
-                        float normalLength = Math.Max(0.0f, Math.Min(1.0f, averageNormal.magnitude));
-                        c[outputPosition].a = normalLength;
+                        c[outputPosition].b = averageNormalLength;
+                        c[outputPosition].a = 1.0f;
+            }
+
+            // Now overwrite the first mip average normal channel - order is important as above we read the mip0
+            // For mip 0, set the normal length to 1.
+            {
+                Color[] c = texture.GetPixels(0);
+                for (int i = 0; i < c.Length; i++)
+                {
+                    c[i].b = 1.0f;
+                    c[i].a = 1.0f;
+                }
+                texture.SetPixels(c, 0);
             }
         }
     }

com.unity.render-pipelines.high-definition/HDRP/Editor/Material/StackLit/StackLitUI.cs

         protected const string kStencilRefMV = "_StencilRefMV";
         protected const string kStencilWriteMaskMV = "_StencilWriteMaskMV";
 
-        protected const string k_SpecularAntiAliasingEnabled = "_SpecularAntiAliasingEnabled";
+        protected const string k_GeometricNormalFilteringEnabled = "_GeometricNormalFilteringEnabled";
+        protected const string k_TextureNormalFilteringEnabled = "_TextureNormalFilteringEnabled";        
 
         #endregion
 
         private Property EnableDualSpecularLobe;
         private Property EnableIridescence;
 
-        private Property EnableSpecularAA;
+        private Property EnableGeometricNormalFiltering;
+        private Property EnableTextureNormalFiltering;
 
         public StackLitGUI()
         {
             EnableDualSpecularLobe = new Property(this, k_EnableDualSpecularLobe, "Enable Dual Specular Lobe", "Enable a second specular lobe, aim to simulate a mix of a narrow and a haze lobe that better match measured material", true);
             EnableIridescence = new Property(this, k_EnableIridescence, "Enable Iridescence", "Enable physically based iridescence layer", true);
 
-            EnableSpecularAA = new Property(this, k_SpecularAntiAliasingEnabled, "Enable SpecularAA", "Enable specular antialiasing", true);
+            EnableGeometricNormalFiltering = new Property(this, k_GeometricNormalFilteringEnabled, "Enable Geometric filtering", "Enable specular antialiasing", true);
+            EnableTextureNormalFiltering = new Property(this, k_TextureNormalFilteringEnabled, "Enable Texture filtering", "Require normal map to use _NA or _OSNA suffix for normal map name", true);
 
             // All material properties
             // All GroupPropery below need to define a
                     new Property(this, k_AlbedoAffectEmissive, "Albedo Affect Emissive", "Specifies whether or not the emissive color is multiplied by the albedo.", false),
                 }),
 
-                new GroupProperty(this, "_SpecularAntiAliasing", "SpecularAntiAliasing", new BaseProperty[]
+                new GroupProperty(this, "_SpecularAntiAliasing", "Specular Anti-Aliasing", new BaseProperty[]
-                    EnableSpecularAA,
-                    new Property(this, "_SpecularAntiAliasingScreenSpaceVariance", "Screen Space Variance", "Screen Space Variance (should be less than 0.25)", false, _ => EnableSpecularAA.BoolValue == true),
-                    new Property(this, "_SpecularAntiAliasingThreshold", "Threshold", "Threshold", false, _ => EnableSpecularAA.BoolValue == true),
+                    EnableTextureNormalFiltering,
+                    EnableGeometricNormalFiltering,
+                    new Property(this, "_SpecularAntiAliasingThreshold", "Threshold", "Threshold", false, _ => (EnableGeometricNormalFiltering.BoolValue || EnableTextureNormalFiltering.BoolValue) == true),
+                    new Property(this, "_SpecularAntiAliasingScreenSpaceVariance", "Screen Space Variance", "Screen Space Variance (should be less than 0.25)", false, _ => EnableGeometricNormalFiltering.BoolValue == true),
                 }),
 
                 new GroupProperty(this, "_Debug", "Debug", new BaseProperty[]

com.unity.render-pipelines.high-definition/HDRP/Material/LayeredLit/LayeredLitData.hlsl

 
 #ifdef _ENABLE_GEOMETRIC_SPECULAR_AA
     // Specular AA
-    surfaceData.perceptualSmoothness = GeometricFilterPerceptualSmoothness(surfaceData.perceptualSmoothness, input.worldToTangent[2], _SpecularAAScreenSpaceVariance, _SpecularAAThreshold);
+    surfaceData.perceptualSmoothness = GeometricNormalFiltering(surfaceData.perceptualSmoothness, input.worldToTangent[2], _SpecularAAScreenSpaceVariance, _SpecularAAThreshold);
 #endif
 
     GetBuiltinData(input, surfaceData, alpha, bentNormalWS, depthOffset, builtinData);

com.unity.render-pipelines.high-definition/HDRP/Material/Lit/LitData.hlsl

 
 #ifdef _ENABLE_GEOMETRIC_SPECULAR_AA
     // Specular AA
-    surfaceData.perceptualSmoothness = GeometricFilterPerceptualSmoothness(surfaceData.perceptualSmoothness, input.worldToTangent[2], _SpecularAAScreenSpaceVariance, _SpecularAAThreshold);
+    surfaceData.perceptualSmoothness = GeometricNormalFiltering(surfaceData.perceptualSmoothness, input.worldToTangent[2], _SpecularAAScreenSpaceVariance, _SpecularAAThreshold);
 #endif
 
     // Caution: surfaceData must be fully initialize before calling GetBuiltinData

com.unity.render-pipelines.high-definition/HDRP/Material/StackLit/StackLit.shader

         [HideInInspector] _ZTestDepthEqualForOpaque("_ZTestDepthEqualForOpaque", Int) = 4 // Less equal
         [HideInInspector] _ZTestModeDistortion("_ZTestModeDistortion", Int) = 8
 
-        [ToggleUI] _SpecularAntiAliasingEnabled("Specular Anti Aliasing Enabled", Float) = 0.0
+        [ToggleUI] _GeometricNormalFilteringEnabled("GeometricNormalFilteringEnabled", Float) = 0.0
+        [ToggleUI] _TextureNormalFilteringEnabled("TextureNormalFilteringEnabled", Float) = 0.0
         _SpecularAntiAliasingScreenSpaceVariance("SpecularAntiAliasingScreenSpaceVariance", Range(0.0, 1.0)) = 0.1
         _SpecularAntiAliasingThreshold("SpecularAntiAliasingThreshold", Range(0.0, 1.0)) = 0.2
 

com.unity.render-pipelines.high-definition/HDRP/Material/StackLit/StackLitData.hlsl

 
         // We forbid scale in case of object space as it make no sense
         // Decompress normal ourselve
-        float3 normalOS = SampleTexture2DTriplanarScaleBias(TEXTURE2D_PARAM(textureName, samplerName), textureNameUV, textureNameUVLocal, textureNameST, uvMapping).xyz * 2.0 - 1.0;
+        float4 packedNormal = SampleTexture2DTriplanarScaleBias(TEXTURE2D_PARAM(textureName, samplerName), textureNameUV, textureNameUVLocal, textureNameST, uvMapping);
+        float3 normalOS = packedNormal.xyz * 2.0 - 1.0;
+        float averageNormalLength = packedNormal.w; // If we used a object space normal map that store average normal, the formap is RGB (normal xyz) and A (average normal length)
-        return float4(SurfaceGradientFromPerturbedNormal(uvMapping.vertexNormalWS, TransformObjectToWorldDir(normalOS)), 1.0);
+        return float4(SurfaceGradientFromPerturbedNormal(uvMapping.vertexNormalWS, TransformObjectToWorldDir(normalOS)), averageNormalLength);
     }
     else
     {
             float2 derivYPlane;
             float2 derivZPlane;
             derivXplane = derivYPlane = derivZPlane = float2(0.0, 0.0);
+            float averageNormalLength = 0.0;
-                derivXplane = uvMapping.triplanarWeights[textureNameUVLocal].x * UnpackDerivativeNormalRGorAG(SampleTexture2DScaleBias(TEXTURE2D_PARAM(textureName, samplerName), TEXCOORD_INDEX_PLANAR_YZ, textureNameUVLocal, textureNameST, uvMapping), scale);
+            {
+                float4 packedNormal = SampleTexture2DScaleBias(TEXTURE2D_PARAM(textureName, samplerName), TEXCOORD_INDEX_PLANAR_YZ, textureNameUVLocal, textureNameST, uvMapping);
+                averageNormalLength += uvMapping.triplanarWeights[textureNameUVLocal].x * packedNormal.z;
+                derivXplane = uvMapping.triplanarWeights[textureNameUVLocal].x * UnpackDerivativeNormalRGorAG(packedNormal, scale);
+            }
-                derivYPlane = uvMapping.triplanarWeights[textureNameUVLocal].y * UnpackDerivativeNormalRGorAG(SampleTexture2DScaleBias(TEXTURE2D_PARAM(textureName, samplerName), TEXCOORD_INDEX_PLANAR_ZX, textureNameUVLocal, textureNameST, uvMapping), scale);
+            {
+                float4 packedNormal = SampleTexture2DScaleBias(TEXTURE2D_PARAM(textureName, samplerName), TEXCOORD_INDEX_PLANAR_ZX, textureNameUVLocal, textureNameST, uvMapping);
+                averageNormalLength += uvMapping.triplanarWeights[textureNameUVLocal].y * packedNormal.z;
+                derivYPlane = uvMapping.triplanarWeights[textureNameUVLocal].y * UnpackDerivativeNormalRGorAG(packedNormal, scale);
+            }
-                derivZPlane = uvMapping.triplanarWeights[textureNameUVLocal].z * UnpackDerivativeNormalRGorAG(SampleTexture2DScaleBias(TEXTURE2D_PARAM(textureName, samplerName), TEXCOORD_INDEX_PLANAR_XY, textureNameUVLocal, textureNameST, uvMapping), scale);
+            {
+                float4 packedNormal = SampleTexture2DScaleBias(TEXTURE2D_PARAM(textureName, samplerName), TEXCOORD_INDEX_PLANAR_XY, textureNameUVLocal, textureNameST, uvMapping);
+                averageNormalLength += uvMapping.triplanarWeights[textureNameUVLocal].z * packedNormal.z;
+                derivZPlane = uvMapping.triplanarWeights[textureNameUVLocal].z * UnpackDerivativeNormalRGorAG(packedNormal, scale);
+            }
-            return float4(SurfaceGradientFromVolumeGradient(uvMapping.vertexNormalWS, volumeGrad), 1.0);
+            return float4(SurfaceGradientFromVolumeGradient(uvMapping.vertexNormalWS, volumeGrad), averageNormalLength);
-        float2 deriv = UnpackDerivativeNormalRGorAG(SampleTexture2DScaleBias(TEXTURE2D_PARAM(textureName, samplerName), textureNameUV, textureNameUVLocal, textureNameST, uvMapping), scale);
+        float4 packedNormal = SampleTexture2DScaleBias(TEXTURE2D_PARAM(textureName, samplerName), textureNameUV, textureNameUVLocal, textureNameST, uvMapping);
+        float averageNormalLength = packedNormal.z; // If we used a tangent space normal map that store average normal, the formap is RG (normal xy) and B (average normal length)
+        float2 deriv = UnpackDerivativeNormalRGorAG(packedNormal, scale);
-            return float4(SurfaceGradientFromTBN(deriv, uvMapping.vertexTangentWS[textureNameUV], uvMapping.vertexBitangentWS[textureNameUV]), 1.0);
+            return float4(SurfaceGradientFromTBN(deriv, uvMapping.vertexTangentWS[textureNameUV], uvMapping.vertexBitangentWS[textureNameUV]), averageNormalLength);
         }
         else
         {
             else if (textureNameUV == TEXCOORD_INDEX_PLANAR_XY)
                 volumeGrad = float3(deriv.x, deriv.y, 0.0);
 
-            return float4(SurfaceGradientFromVolumeGradient(uvMapping.vertexNormalWS, volumeGrad), 1.0f);
+            return float4(SurfaceGradientFromVolumeGradient(uvMapping.vertexNormalWS, volumeGrad), averageNormalLength);
         }
     }
 }
     surfaceData.normalWS = SurfaceGradientResolveNormal(input.worldToTangent[2], gradient.xyz);
     surfaceData.coatNormalWS = SurfaceGradientResolveNormal(input.worldToTangent[2], coatGradient.xyz);
 
-    if (_SpecularAntiAliasingEnabled > 0.0)
+    if ((_GeometricNormalFilteringEnabled + _TextureNormalFilteringEnabled) > 0.0)
-        float geometricVariance = GeometricFilterVariance(input.worldToTangent[2], _SpecularAntiAliasingScreenSpaceVariance);
-        float textureFilteringVariance = TextureFilteringVariance(gradient.w);
-        float coatTextureFilteringVariance = TextureFilteringVariance(coatGradient.w);
+        float geometricVariance = _GeometricNormalFilteringEnabled ? GeometricNormalVariance(input.worldToTangent[2], _SpecularAntiAliasingScreenSpaceVariance) : 0.0;
+        // gradient.w is the average normal length
+        float textureFilteringVariance = _TextureNormalFilteringEnabled ? TextureNormalVariance(gradient.w) : 0.0;
+        float coatTextureFilteringVariance = _TextureNormalFilteringEnabled ? TextureNormalVariance(coatGradient.w) : 0.0;
-        surfaceData.perceptualSmoothnessA = FilterPerceptualSmoothness(surfaceData.perceptualSmoothnessA, geometricVariance + textureFilteringVariance, _SpecularAntiAliasingThreshold);
-        surfaceData.perceptualSmoothnessB = FilterPerceptualSmoothness(surfaceData.perceptualSmoothnessB, geometricVariance + textureFilteringVariance, _SpecularAntiAliasingThreshold);
-        surfaceData.coatPerceptualSmoothness = FilterPerceptualSmoothness(surfaceData.coatPerceptualSmoothness, geometricVariance + coatTextureFilteringVariance, _SpecularAntiAliasingThreshold);
+        surfaceData.perceptualSmoothnessA = NormalFiltering(surfaceData.perceptualSmoothnessA, geometricVariance + textureFilteringVariance, _SpecularAntiAliasingThreshold);
+        surfaceData.perceptualSmoothnessB = NormalFiltering(surfaceData.perceptualSmoothnessB, geometricVariance + textureFilteringVariance, _SpecularAntiAliasingThreshold);
+        surfaceData.coatPerceptualSmoothness = NormalFiltering(surfaceData.coatPerceptualSmoothness, geometricVariance + coatTextureFilteringVariance, _SpecularAntiAliasingThreshold);
     }
 
     // TODO: decal etc.

com.unity.render-pipelines.high-definition/HDRP/Material/StackLit/StackLitProperties.hlsl

 float _EmissiveIntensity;
 float _AlbedoAffectEmissive;
 
-float _SpecularAntiAliasingEnabled;
+float _GeometricNormalFilteringEnabled;
+float _TextureNormalFilteringEnabled;
 float _SpecularAntiAliasingScreenSpaceVariance;
 float _SpecularAntiAliasingThreshold;