[10.x.x] Axf fix shininess exp to roughness, ssr transparent and alpha test #587

Author: slunity

TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/WindowsEditor/Vulkan/None/1451_AxF_SVBRDF.png

@@ -59,6 +59,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Tentative fix for missing include in depth of field shaders.
 - Fixed Wizard check on default volume profile to also check it is not the default one in package.
 - Fixed light layers not correctly disabled when the lightlayers is set to Nothing and Lightlayers isn't enabled in HDRP Asset
+- Fixed AxF handling of roughness for Blinn-Phong type materials
+- Fixed AxF UI errors when surface type is switched to transparent
 
 ### Changed
 - Shadowmask and realtime reflection probe property are hide in Quality settings

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -132,8 +132,13 @@ static public void SetupMaterialKeywordsAndPass(Material material)
             // Keywords for opt-out of decals and SSR:
             bool decalsEnabled = material.HasProperty(kEnableDecals) && material.GetFloat(kEnableDecals) > 0.0f;
             CoreUtils.SetKeyword(material, "_DISABLE_DECALS", decalsEnabled == false);
-            bool ssrEnabled = material.HasProperty(kEnableSSR) && material.GetFloat(kEnableSSR) > 0.0f;
-            CoreUtils.SetKeyword(material, "_DISABLE_SSR", ssrEnabled == false);
+            bool ssrEnabled = false;
+            if (material.GetSurfaceType() == SurfaceType.Transparent)
+                ssrEnabled = material.HasProperty(kReceivesSSRTransparent) ? material.GetFloat(kReceivesSSRTransparent) != 0 : false;
+            else
+                ssrEnabled = material.HasProperty(kReceivesSSR) ? material.GetFloat(kReceivesSSR) != 0 : false;
+            CoreUtils.SetKeyword(material, "_DISABLE_SSR", material.HasProperty(kReceivesSSR) && material.GetFloat(kReceivesSSR) == 0.0f);
+            CoreUtils.SetKeyword(material, "_DISABLE_SSR_TRANSPARENT", material.HasProperty(kReceivesSSRTransparent) && material.GetFloat(kReceivesSSRTransparent) == 0.0);
             CoreUtils.SetKeyword(material, "_ENABLE_GEOMETRIC_SPECULAR_AA", material.HasProperty(kEnableGeometricSpecularAA) && material.GetFloat(kEnableGeometricSpecularAA) > 0.0f);
             CoreUtils.SetKeyword(material, "_SPECULAR_OCCLUSION_NONE", material.HasProperty(kSpecularOcclusionMode) && material.GetFloat(kSpecularOcclusionMode) == 0.0f);
 

com.unity.render-pipelines.high-definition/Editor/Material/AxF/AxFGUI.cs

@@ -1175,7 +1175,8 @@ PreLightData    GetPreLightData(float3 viewWS_Clearcoat, PositionInputs posInput
         preLightData.iblPerceptualRoughness = PerceptualRoughnessBeckmannToGGX(preLightData.iblPerceptualRoughness);
         break;
 
-    // case 1: // @TODO: Support Blinn-Phong FGD?
+    case 1: //Phong
+    case 4: //Blinn-Phong : just approximate with Cook-Torrance which uses a Beckmann distribution
     case 2:
         GetPreIntegratedFGDCookTorranceAndLambert(NdotV_UnderCoat, preLightData.iblPerceptualRoughness, tempF0, preLightData.specularFGD, preLightData.diffuseFGD, specularReflectivity);
         preLightData.specularFGD *= GetPreIntegratedFGDCookTorranceSampleMutiplier();
@@ -1186,8 +1187,6 @@ PreLightData    GetPreLightData(float3 viewWS_Clearcoat, PositionInputs posInput
         GetPreIntegratedFGDGGXAndLambert(NdotV_UnderCoat, preLightData.iblPerceptualRoughness, tempF0, preLightData.specularFGD, preLightData.diffuseFGD, specularReflectivity);
         break;
 
-     // case 4: // @TODO: Support Blinn-Phong FGD?
-
     default:    // Use GGX by default
         GetPreIntegratedFGDGGXAndLambert(NdotV_UnderCoat, preLightData.iblPerceptualRoughness, tempF0, preLightData.specularFGD, preLightData.diffuseFGD, specularReflectivity);
         break;
@@ -1356,14 +1355,6 @@ PreLightData    GetPreLightData(float3 viewWS_Clearcoat, PositionInputs posInput
     case 1: // BLINN-PHONG
     case 4: // PHONG;
     {
-        // According to https://computergraphics.stackexchange.com/questions/1515/what-is-the-accepted-method-of-converting-shininess-to-roughness-and-vice-versa
-        //  float   exponent = 2/roughness^4 - 2;
-        //
-        float   exponent = PerceptualRoughnessToRoughness(preLightData.iblPerceptualRoughness);
-        float   roughness = pow(max(0.0, 2.0 / (exponent + 2)), 1.0 / 4.0);
-        // todo_modes todo_pseudorefract: cant use undercoat like that
-        //float2  UV = LTCGetSamplingUV(NdotV_UnderCoat, RoughnessToPerceptualRoughness(roughness));
-        float2  UV = LTCGetSamplingUV(NdotV_Clearcoat, RoughnessToPerceptualRoughness(roughness));
         preLightData.ltcTransformSpecular = LTCSampleMatrix(UV, LTC_MATRIX_INDEX_COOK_TORRANCE);
         break;
     }
@@ -1576,7 +1567,8 @@ float3 ComputeWard(float3 H, float LdotH, float NdotL, float NdotV, PreLightData
 
 float3  ComputeBlinnPhong(float3 H, float LdotH, float NdotL, float NdotV, PreLightData preLightData, BSDFData bsdfData)
 {
-    float2  exponents = exp2(bsdfData.roughness.xy);
+    // See AxFGetRoughnessFromSpecularLobeTexture in AxFData
+    float2  exponents = 2 * rcp(max(0.0001,(bsdfData.roughness.xy*bsdfData.roughness.xy))) - 2;
 
     // Evaluate normal distribution function
     float3  tsH = float3(dot(H, bsdfData.tangentWS), dot(H, bsdfData.biTangentWS), dot(H, bsdfData.normalWS));

com.unity.render-pipelines.high-definition/Runtime/Material/AxF/AxF.hlsl

@@ -141,7 +141,7 @@ Shader "HDRP/AxF"
 
         [ToggleUI] _SupportDecals("Support Decals", Float) = 1.0
         [ToggleUI] _ReceivesSSR("Receives SSR", Float) = 1.0
-
+        [ToggleUI] _ReceivesSSRTransparent("Receives SSR Transparent", Float) = 0.0
         [ToggleUI] _AddPrecomputedVelocity("AddPrecomputedVelocity", Float) = 0.0
 
     }
@@ -167,6 +167,7 @@ Shader "HDRP/AxF"
 
     #pragma shader_feature_local _DISABLE_DECALS
     #pragma shader_feature_local _DISABLE_SSR
+    #pragma shader_feature_local _DISABLE_SSR_TRANSPARENT
     #pragma shader_feature_local _ENABLE_GEOMETRIC_SPECULAR_AA
 
     #pragma shader_feature_local _ADD_PRECOMPUTED_VELOCITY

com.unity.render-pipelines.high-definition/Runtime/Material/AxF/AxF.shader

@@ -464,6 +464,29 @@ void ApplyDecalToSurfaceData(DecalSurfaceData decalSurfaceData, inout SurfaceDat
 #endif
 }
 
+bool HasPhongTypeBRDF()
+{
+    uint type = ((_SVBRDF_BRDFType >> 1) & 7);
+    return type == 1 || type == 4;
+}
+
+float2 AxFGetRoughnessFromSpecularLobeTexture(float2 specularLobe)
+{
+    // For Blinn-Phong, AxF encodes specularLobe.xy as log2(shiniExp_xy) so
+    //     shiniExp = exp2(abs(specularLobe.xy))
+    // A good fit for a corresponding Beckmann roughness is
+    //     roughnessBeckmann^2 = 2 /(shiniExp + 2)
+    // See eg
+    // http://graphicrants.blogspot.com/2013/08/specular-brdf-reference.html
+    // http://simonstechblog.blogspot.com/2011/12/microfacet-brdf.html
+
+    // We thus have 
+    //     roughnessBeckmann = sqrt(2) * rsqrt(exp2(abs(specularLobe.xy)) + 2);
+    //     shiniExp = 2 * rcp(max(0.0001,(roughnessBeckmann*roughnessBeckmann))) - 2;
+
+    return (HasPhongTypeBRDF() ? (sqrt(2) * rsqrt(exp2(abs(specularLobe)) + 2)) : specularLobe);
+}
+
 void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs posInput, out SurfaceData surfaceData, out BuiltinData builtinData)
 {
 #ifdef _DOUBLESIDED_ON
@@ -479,8 +502,18 @@ void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs p
     InitTextureUVMapping(input, uvMapping);
     ZERO_INITIALIZE(SurfaceData, surfaceData);
 
+    float alpha = AXF_SAMPLE_SMP_TEXTURE2D(_SVBRDF_AlphaMap, sampler_SVBRDF_AlphaMap, uvMapping).x;
+
+#ifdef _ALPHATEST_ON
+    // TODOTODO: Move alpha test earlier and test.
+    float alphaCutoff = _AlphaCutoff;
 
-    float alpha = 1.0;
+    #if SHADERPASS == SHADERPASS_SHADOWS 
+        GENERIC_ALPHA_TEST(alpha, _UseShadowThreshold ? _AlphaCutoffShadow : alphaCutoff);
+    #else
+        GENERIC_ALPHA_TEST(alpha, alphaCutoff);
+    #endif
+#endif
 
     surfaceData.ambientOcclusion = 1.0;
     surfaceData.specularOcclusion = 1.0;
@@ -494,7 +527,8 @@ void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs p
 
     surfaceData.diffuseColor = AXF_SAMPLE_SMP_TEXTURE2D(_SVBRDF_DiffuseColorMap, sampler_SVBRDF_DiffuseColorMap, uvMapping).xyz;
     surfaceData.specularColor = AXF_SAMPLE_SMP_TEXTURE2D(_SVBRDF_SpecularColorMap, sampler_SVBRDF_SpecularColorMap, uvMapping).xyz;
-    surfaceData.specularLobe.xy = _SVBRDF_SpecularLobeMapScale * AXF_SAMPLE_SMP_TEXTURE2D(_SVBRDF_SpecularLobeMap, sampler_SVBRDF_SpecularLobeMap, uvMapping).xy;
+    surfaceData.specularLobe.xy = _SVBRDF_SpecularLobeMapScale * AxFGetRoughnessFromSpecularLobeTexture(
+        AXF_SAMPLE_SMP_TEXTURE2D(_SVBRDF_SpecularLobeMap, sampler_SVBRDF_SpecularLobeMap, uvMapping).xy);
 
     // The AxF models include both a general coloring term that they call "specular color" while the f0 is actually another term,
     // seemingly always scalar:
@@ -524,8 +558,6 @@ void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs p
     // Useless for SVBRDF, will be optimized out
     //SetFlakesSurfaceData(uvMapping, surfaceData);
 
-    alpha = AXF_SAMPLE_SMP_TEXTURE2D(_SVBRDF_AlphaMap, sampler_SVBRDF_AlphaMap, uvMapping).x;
-
     //-----------------------------------------------------------------------------
     // _AXF_BRDF_TYPE_CAR_PAINT
     //-----------------------------------------------------------------------------
@@ -604,17 +636,6 @@ void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs p
     // the handedness of the world space (tangentToWorld can be passed right handed while
     // Unity's WS is left handed, so this makes a difference here).
 
-#ifdef _ALPHATEST_ON
-    // TODOTODO: Move alpha test earlier and test.
-    float alphaCutoff = _AlphaCutoff;
-
-    #if SHADERPASS == SHADERPASS_SHADOWS 
-        GENERIC_ALPHA_TEST(alpha, _UseShadowThreshold ? _AlphaCutoffShadow : alphaCutoff);
-    #else
-        GENERIC_ALPHA_TEST(alpha, alphaCutoff);
-    #endif
-#endif
-
 #if defined(_ENABLE_GEOMETRIC_SPECULAR_AA)
     // Specular AA for geometric curvature