make PartitionRandVar in struct and templated

Author: keptsecret

examples_tests

@@ -8,6 +8,7 @@
 #include "nbl/builtin/hlsl/bxdf/config.hlsl"
 #include "nbl/builtin/hlsl/bxdf/ndf.hlsl"
 #include "nbl/builtin/hlsl/bxdf/fresnel.hlsl"
+#include "nbl/builtin/hlsl/sampling/basic.hlsl"
 #include "nbl/builtin/hlsl/bxdf/ndf/microfacet_to_light_transform.hlsl"
 
 namespace nbl
@@ -302,7 +303,8 @@ struct SCookTorrance
 
         scalar_type rcpChoiceProb;
         scalar_type z = u.z;
-        bool transmitted = math::partitionRandVariable(reflectance, z, rcpChoiceProb);
+        sampling::PartitionRandVariable<scalar_type> partitionRandVariable;
+        bool transmitted = partitionRandVariable(reflectance, z, rcpChoiceProb);
 
         const scalar_type LdotH = hlsl::mix(VdotH, ieee754::copySign(hlsl::sqrt(rcpEta.value2[0]*VdotH*VdotH + scalar_type(1.0) - rcpEta.value2[0]), -VdotH), transmitted);
         bool valid;

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

@@ -6,6 +6,7 @@
 
 #include "nbl/builtin/hlsl/bxdf/common.hlsl"
 #include "nbl/builtin/hlsl/bxdf/bxdf_traits.hlsl"
+#include "nbl/builtin/hlsl/sampling/basic.hlsl"
 #include "nbl/builtin/hlsl/sampling/cos_weighted_spheres.hlsl"
 
 namespace nbl
@@ -39,7 +40,8 @@ struct SSmoothDielectric
         const scalar_type reflectance = fresnel::Dielectric<monochrome_type>::__call(orientedEta.value*orientedEta.value, interaction.getNdotV(_clamp))[0];
 
         scalar_type rcpChoiceProb;
-        bool transmitted = math::partitionRandVariable(reflectance, u.z, rcpChoiceProb);
+        sampling::PartitionRandVariable<scalar_type> partitionRandVariable;
+        bool transmitted = partitionRandVariable(reflectance, u.z, rcpChoiceProb);
 
         ray_dir_info_type V = interaction.getV();
         Refract<scalar_type> r = Refract<scalar_type>::create(V.getDirection(), interaction.getN());
@@ -125,7 +127,8 @@ struct SThinSmoothDielectric
 
         scalar_type rcpChoiceProb;
         scalar_type z = u.z;
-        const bool transmitted = math::partitionRandVariable(reflectionProb, z, rcpChoiceProb);
+        sampling::PartitionRandVariable<scalar_type> partitionRandVariable;
+        const bool transmitted = partitionRandVariable(reflectionProb, z, rcpChoiceProb);
         remainderMetadata = hlsl::mix(reflectance, hlsl::promote<spectral_type>(1.0) - reflectance, transmitted) * rcpChoiceProb;
 
         ray_dir_info_type V = interaction.getV();

include/nbl/builtin/hlsl/bxdf/transmission/smooth_dielectric.hlsl

@@ -120,21 +120,6 @@ void frisvad(NBL_CONST_REF_ARG(T) normal, NBL_REF_ARG(T) tangent, NBL_REF_ARG(T)
     }
 }
 
-bool partitionRandVariable(float leftProb, NBL_REF_ARG(float) xi, NBL_REF_ARG(float) rcpChoiceProb)
-{
-    const float32_t NEXT_ULP_AFTER_UNITY = bit_cast<float32_t>(0x3f800001u);
-    const bool pickRight = xi >= leftProb * NEXT_ULP_AFTER_UNITY;
-
-    // This is all 100% correct taking into account the above NEXT_ULP_AFTER_UNITY
-    xi -= pickRight ? leftProb : 0.0f;
-
-    rcpChoiceProb = 1.0f / (pickRight ? (1.0f - leftProb) : leftProb);
-    xi *= rcpChoiceProb;
-
-    return pickRight;
-}
-
-
 namespace impl
 {
 template <typename T NBL_STRUCT_CONSTRAINABLE>

include/nbl/builtin/hlsl/math/functions.hlsl

@@ -0,0 +1,44 @@
+// Copyright (C) 2018-2025 - DevSH Graphics Programming Sp. z O.O.
+// This file is part of the "Nabla Engine".
+// For conditions of distribution and use, see copyright notice in nabla.h
+
+#ifndef _NBL_BUILTIN_HLSL_SAMPLING_BASIC_INCLUDED_
+#define _NBL_BUILTIN_HLSL_SAMPLING_BASIC_INCLUDED_
+
+#include <nbl/builtin/hlsl/cpp_compat.hlsl>
+#include <nbl/builtin/hlsl/ieee754.hlsl>
+
+namespace nbl
+{
+namespace hlsl
+{
+namespace sampling
+{
+
+template<typename T NBL_PRIMARY_REQUIRES(concepts::FloatingPointLikeScalar<T>)
+struct PartitionRandVariable
+{
+    using floating_point_type = T;
+    using uint_type = typename unsigned_integer_of_size<sizeof(floating_point_type)>::type;
+
+    bool operator()(floating_point_type leftProb, NBL_REF_ARG(floating_point_type) xi, NBL_REF_ARG(floating_point_type) rcpChoiceProb)
+    {
+        const floating_point_type NEXT_ULP_AFTER_UNITY = bit_cast<floating_point_type>(bit_cast<uint_type>(floating_point_type(1.0)) + uint_type(1u));
+        const bool pickRight = xi >= leftProb * NEXT_ULP_AFTER_UNITY;
+
+        // This is all 100% correct taking into account the above NEXT_ULP_AFTER_UNITY
+        xi -= pickRight ? leftProb : floating_point_type(0.0);
+
+        rcpChoiceProb = floating_point_type(1.0) / (pickRight ? (floating_point_type(1.0) - leftProb) : leftProb);
+        xi *= rcpChoiceProb;
+
+        return pickRight;
+    }
+};
+
+
+}
+}
+}
+
+#endif

include/nbl/builtin/hlsl/sampling/basic.hlsl

@@ -253,6 +253,7 @@ LIST_BUILTIN_RESOURCE(NBL_RESOURCES_TO_EMBED "hlsl/shapes/spherical_triangle.hls
 LIST_BUILTIN_RESOURCE(NBL_RESOURCES_TO_EMBED "hlsl/shapes/spherical_rectangle.hlsl")
 LIST_BUILTIN_RESOURCE(NBL_RESOURCES_TO_EMBED "hlsl/shapes/aabb.hlsl")
 #sampling
+LIST_BUILTIN_RESOURCE(NBL_RESOURCES_TO_EMBED "hlsl/sampling/basic.hlsl")
 LIST_BUILTIN_RESOURCE(NBL_RESOURCES_TO_EMBED "hlsl/sampling/linear.hlsl")
 LIST_BUILTIN_RESOURCE(NBL_RESOURCES_TO_EMBED "hlsl/sampling/bilinear.hlsl")
 LIST_BUILTIN_RESOURCE(NBL_RESOURCES_TO_EMBED "hlsl/sampling/concentric_mapping.hlsl")