various fixes to ggx ndf, cook torrance base

Author: keptsecret

include/nbl/builtin/hlsl/bxdf/base/cook_torrance_base.hlsl

@@ -69,28 +69,29 @@ struct quant_query_helper<N, F, false>
 };
 
 template<class F, bool IsBSDF>
-struct check_TIR_helper;
+struct checkValid;
 
 template<class F>
-struct check_TIR_helper<F, false>
+struct checkValid<F, false>
 {
-    template<class MicrofacetCache>
-    static bool __call(NBL_CONST_REF_ARG(F) fresnel, NBL_CONST_REF_ARG(MicrofacetCache) cache)
+    using scalar_type = typename F::scalar_type;
+
+    template<class Sample, class Interaction, class MicrofacetCache>
+    static bool __call(NBL_CONST_REF_ARG(F) fresnel, NBL_CONST_REF_ARG(Sample) _sample, NBL_CONST_REF_ARG(Interaction) interaction, NBL_CONST_REF_ARG(MicrofacetCache) cache)
     {
-        return true;
+        return _sample.getNdotL() > numeric_limits<scalar_type>::min && interaction.getNdotV() > numeric_limits<scalar_type>::min;
     }
 };
 
 template<class F>
-struct check_TIR_helper<F, true>
+struct checkValid<F, true>
 {
     using vector_type = typename F::vector_type;    // expect monochrome
 
-    template<class MicrofacetCache>
-    static bool __call(NBL_CONST_REF_ARG(F) fresnel, NBL_CONST_REF_ARG(MicrofacetCache) cache)
+    template<class Sample, class Interaction, class MicrofacetCache>
+    static bool __call(NBL_CONST_REF_ARG(F) fresnel, NBL_CONST_REF_ARG(Sample) _sample, NBL_CONST_REF_ARG(Interaction) interaction, NBL_CONST_REF_ARG(MicrofacetCache) cache)
     {
-        fresnel::OrientedEtas<vector_type> orientedEta = fresnel::OrientedEtas<vector_type>::create(typename F::scalar_type(1.0), hlsl::promote<vector_type>(fresnel.getRefractionOrientedEta()));
-        return cache.isValid(orientedEta);
+        return cache.isValid(fresnel.getRefractionOrientedEta());
     }
 };
 
@@ -135,22 +136,13 @@ struct SCookTorrance
     NBL_CONSTEXPR_STATIC_INLINE bool IsBSDF = ndf_type::SupportedPaths != ndf::MTT_REFLECT;
     NBL_HLSL_BXDF_ANISOTROPIC_COND_DECLS(IsAnisotropic);
 
-    template<class Interaction, class MicrofacetCache>
-    static bool __checkValid(NBL_CONST_REF_ARG(fresnel_type) f, NBL_CONST_REF_ARG(sample_type) _sample, NBL_CONST_REF_ARG(Interaction) interaction, NBL_CONST_REF_ARG(MicrofacetCache) cache)
-    {
-        NBL_IF_CONSTEXPR(IsBSDF)
-            return impl::check_TIR_helper<fresnel_type, IsBSDF>::template __call<MicrofacetCache>(f, cache);
-        else
-            return _sample.getNdotL() > numeric_limits<scalar_type>::min && interaction.getNdotV() > numeric_limits<scalar_type>::min;
-    }
-
     template<class Interaction=conditional_t<IsAnisotropic,anisotropic_interaction_type,isotropic_interaction_type>, 
             class MicrofacetCache=conditional_t<IsAnisotropic,anisocache_type,isocache_type>
             NBL_FUNC_REQUIRES(RequiredInteraction<Interaction> && RequiredMicrofacetCache<MicrofacetCache>)
     spectral_type eval(NBL_CONST_REF_ARG(sample_type) _sample, NBL_CONST_REF_ARG(Interaction) interaction, NBL_CONST_REF_ARG(MicrofacetCache) cache)
     {
         fresnel_type _f = impl::getOrientedFresnel<fresnel_type, IsBSDF>::__call(fresnel, interaction.getNdotV());
-        if (!__checkValid<Interaction, MicrofacetCache>(_f, _sample, interaction, cache))
+        if (!impl::checkValid<fresnel_type, IsBSDF>::template __call<sample_type, Interaction, MicrofacetCache>(_f, _sample, interaction, cache))
             return hlsl::promote<spectral_type>(0.0);
 
         using quant_query_type = typename ndf_type::quant_query_type;
@@ -279,8 +271,8 @@ struct SCookTorrance
 
         return sample_type::create(L, T, B, NdotL);
     }
-    template<typename C=bool_constant<!IsAnisotropic>, typename T=conditional_t<IsBSDF, vector3_type, vector2_type> >
-    enable_if_t<C::value && !IsAnisotropic, sample_type> generate(NBL_CONST_REF_ARG(isotropic_interaction_type) interaction, const T u, NBL_REF_ARG(isocache_type) cache)
+    template<typename C=bool_constant<!IsAnisotropic> >
+    enable_if_t<C::value && !IsAnisotropic, sample_type> generate(NBL_CONST_REF_ARG(isotropic_interaction_type) interaction, const conditional_t<IsBSDF, vector3_type, vector2_type> u, NBL_REF_ARG(isocache_type) cache)
     {
         anisocache_type aniso_cache;
         sample_type s = generate(anisotropic_interaction_type::create(interaction), u, aniso_cache);
@@ -315,10 +307,8 @@ struct SCookTorrance
             NBL_FUNC_REQUIRES(RequiredInteraction<Interaction> && RequiredMicrofacetCache<MicrofacetCache>)
     scalar_type pdf(NBL_CONST_REF_ARG(sample_type) _sample, NBL_CONST_REF_ARG(Interaction) interaction, NBL_CONST_REF_ARG(MicrofacetCache) cache)
     {
-        fresnel_type _f = fresnel;
-        NBL_IF_CONSTEXPR(IsBSDF)
-            _f = impl::getOrientedFresnel<fresnel_type, IsBSDF>::__call(fresnel, interaction.getNdotV());
-        if (!__checkValid<anisotropic_interaction_type, anisocache_type>(_f, _sample, interaction, cache))
+        fresnel_type _f = impl::getOrientedFresnel<fresnel_type, IsBSDF>::__call(fresnel, interaction.getNdotV());
+        if (!impl::checkValid<fresnel_type, IsBSDF>::template __call<sample_type, Interaction, MicrofacetCache>(_f, _sample, interaction, cache))
             return scalar_type(0.0);
 
         scalar_type _pdf = __pdf<anisotropic_interaction_type, anisocache_type>(_sample, interaction, cache);
@@ -336,8 +326,8 @@ struct SCookTorrance
         scalar_type _pdf = __pdf<Interaction, MicrofacetCache>(_sample, interaction, cache);
         fresnel_type _f = impl::getOrientedFresnel<fresnel_type, IsBSDF>::__call(fresnel, interaction.getNdotV());
 
-        const bool notTIR = impl::check_TIR_helper<fresnel_type, IsBSDF>::template __call<MicrofacetCache>(_f, cache);
-        assert(notTIR);
+        const bool valid = impl::checkValid<fresnel_type, IsBSDF>::template __call<sample_type, Interaction, MicrofacetCache>(_f, _sample, interaction, cache);
+        assert(valid);
 
         scalar_type G2_over_G1 = scalar_type(1.0);
         if (_pdf < bit_cast<scalar_type>(numeric_limits<scalar_type>::infinity))

include/nbl/builtin/hlsl/bxdf/common.hlsl

@@ -491,7 +491,7 @@ struct SLightSample
 #define NBL_CONCEPT_TPLT_PRM_KINDS (typename)
 #define NBL_CONCEPT_TPLT_PRM_NAMES (T)
 #define NBL_CONCEPT_PARAM_0 (cache, T)
-#define NBL_CONCEPT_PARAM_1 (eta, fresnel::OrientedEtas<vector<typename T::scalar_type,1> >)
+#define NBL_CONCEPT_PARAM_1 (eta, typename T::scalar_type)
 NBL_CONCEPT_BEGIN(2)
 #define cache NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_0
 #define eta NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_1
@@ -664,8 +664,9 @@ struct SIsotropicMicrofacetCache
     // similar with BSDF sampling, as fresnel can be high while reflection can be invalid, or low while refraction would be invalid too
     bool isTransmission() NBL_CONST_MEMBER_FUNC { return getVdotHLdotH() < scalar_type(0.0); }
 
-    bool isValid(NBL_CONST_REF_ARG(fresnel::OrientedEtas<monochrome_type>) orientedEta) NBL_CONST_MEMBER_FUNC
+    bool isValid(const scalar_type eta) NBL_CONST_MEMBER_FUNC
     {
+        fresnel::OrientedEtas<monochrome_type> orientedEta = fresnel::OrientedEtas<monochrome_type>::create(scalar_type(1.0), hlsl::promote<monochrome_type>(eta));
         return ComputeMicrofacetNormal<scalar_type>::isValidMicrofacet(isTransmission(), VdotL, absNdotH, orientedEta);
     }
 
@@ -849,9 +850,9 @@ struct SAnisotropicMicrofacetCache
     scalar_type getNdotH2() NBL_CONST_MEMBER_FUNC { return iso_cache.getNdotH2(); }
     bool isTransmission() NBL_CONST_MEMBER_FUNC { return iso_cache.isTransmission(); }
 
-    bool isValid(NBL_CONST_REF_ARG(fresnel::OrientedEtas<monochrome_type>) orientedEta) NBL_CONST_MEMBER_FUNC
+    bool isValid(const scalar_type eta) NBL_CONST_MEMBER_FUNC
     {
-        return iso_cache.isValid(orientedEta);
+        return iso_cache.isValid(eta);
     }
 
     scalar_type getTdotH() NBL_CONST_MEMBER_FUNC { return TdotH; }

include/nbl/builtin/hlsl/bxdf/ndf/ggx.hlsl

@@ -273,7 +273,7 @@ struct GGX
             dmq.projectedLightMeasure = d * NdotL_over_denominator;
         }
         else
-            dmq.projectedLightMeasure = d * _sample.getNdotL(BxDFClampMode::BCM_MAX);
+            dmq.projectedLightMeasure = d * _sample.getNdotL(BxDFClampMode::BCM_ABS);
         return dmq;
     }
 
@@ -282,7 +282,7 @@ struct GGX
     {
         scalar_type dg1 = scalar_type(0.5) * query.getNdfwoNumerator() * query.getG1over2NdotV();
         quant_type dmq;
-        dmq.microfacetMeasure = dg1;  // note: microfacetMeasure/2NdotV
+        dmq.microfacetMeasure = dg1;  // note: microfacetMeasure/4NdotV
 
         NBL_IF_CONSTEXPR(SupportsTransmission)
         {
@@ -294,7 +294,7 @@ struct GGX
             dmq.projectedLightMeasure = dg1;// TODO: figure this out * NdotL_over_denominator;
         }
         else
-            dmq.projectedLightMeasure = dg1;// TODO: figure this out * _sample.getNdotL(BxDFClampMode::BCM_MAX);
+            dmq.projectedLightMeasure = dg1;// TODO: figure this out * _sample.getNdotL(BxDFClampMode::BCM_ABS);
         return dmq;
     }
 

include/nbl/builtin/hlsl/bxdf/ndf/microfacet_to_light_transform.hlsl

@@ -23,16 +23,35 @@ enum MicrofacetTransformTypes : uint16_t
    MTT_REFLECT_REFRACT = 0b11
 };
 
+namespace microfacet_transform_concepts
+{
+#define NBL_CONCEPT_NAME QuantQuery
+#define NBL_CONCEPT_TPLT_PRM_KINDS (typename)
+#define NBL_CONCEPT_TPLT_PRM_NAMES (T)
+#define NBL_CONCEPT_PARAM_0 (query, T)
+NBL_CONCEPT_BEGIN(1)
+#define query NBL_CONCEPT_PARAM_T NBL_CONCEPT_PARAM_0
+NBL_CONCEPT_END(
+    ((NBL_CONCEPT_REQ_TYPE)(T::scalar_type))
+    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((query.getVdotHLdotH()), ::nbl::hlsl::is_same_v, typename T::scalar_type))
+    ((NBL_CONCEPT_REQ_EXPR_RET_TYPE)((query.getNeg_rcp2_VdotH_etaLdotH()), ::nbl::hlsl::is_same_v, typename T::scalar_type))
+);
+#undef query
+#include <nbl/builtin/hlsl/concepts/__end.hlsl>
+}
+
 template<typename T>
 struct DualMeasureQuantQuery
 {
-    using scalar_type = T;
+   using scalar_type = T;
 
-    scalar_type getVdotHLdotH() NBL_CONST_MEMBER_FUNC { return VdotHLdotH; }
-    scalar_type getNeg_rcp2_VdotH_etaLdotH () NBL_CONST_MEMBER_FUNC { return neg_rcp2_VdotH_etaLdotH ; }
+   // note in pbrt it's `abs(VdotH)*abs(LdotH)`
+   // we leverage the fact that under transmission the sign must always be negative and rest of the code already accounts for that
+   scalar_type getVdotHLdotH() NBL_CONST_MEMBER_FUNC { return VdotHLdotH; }
+   scalar_type getNeg_rcp2_VdotH_etaLdotH () NBL_CONST_MEMBER_FUNC { return neg_rcp2_VdotH_etaLdotH ; }
 
-    scalar_type VdotHLdotH;
-    scalar_type neg_rcp2_VdotH_etaLdotH;
+   scalar_type VdotHLdotH;
+   scalar_type neg_rcp2_VdotH_etaLdotH;
 };