93 lines
3.6 KiB
C++
93 lines
3.6 KiB
C++
#pragma once
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#include "Maths.h"
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namespace dae {
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namespace BRDF {
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/**
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* \param kd Diffuse Reflection Coefficient
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* \param cd Diffuse Color
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* \return Lambert Diffuse Color
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*/
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static ColorRGB Lambert(float kd, const ColorRGB &cd) {
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return (kd / PI) * cd;
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}
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static ColorRGB Lambert(const ColorRGB &kd, const ColorRGB &cd) {
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return (kd * PI) * cd;
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}
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/**
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* \brief todo
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* \param ks Specular Reflection Coefficient
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* \param exp Phong Exponent
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* \param l Incoming (incident) Light Direction
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* \param v View Direction
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* \param n Normal of the Surface
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* \return Phong Specular Color
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*/
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static ColorRGB Phong(float ks, float exp, const Vector3 &l, const Vector3 &v, const Vector3 &n) {
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Vector3 reflect{l - 2 * Vector3::Dot(n, l) * n};
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float cosAngle{Vector3::Dot(reflect, v)};
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return {ks * powf(std::max(0.f, cosAngle), exp) * colors::White};
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}
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/**
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* \brief BRDF Fresnel Function >> Schlick
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* \param h Normalized Halfvector between View and Light directions
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* \param v Normalized View direction
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* \param f0 Base reflectivity of a surface based on IOR (Indices Of Refrection), this is different for Dielectrics (Non-Metal) and Conductors (Metal)
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* \return
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*/
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static ColorRGB FresnelFunction_Schlick(const Vector3 &h, const Vector3 &v, const ColorRGB &f0) {
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const float base = std::pow(1 - Vector3::Dot(h, v), 5);
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auto returnValue{f0 + (colors::White - f0) * base};
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return returnValue;
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}
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/**
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* \brief BRDF NormalDistribution >> Trowbridge-Reitz GGX (UE4 implemetation - squared(roughness))
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* \param n Surface normal
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* \param h Normalized half vector
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* \param roughness Roughness of the material
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* \return BRDF Normal Distribution Term using Trowbridge-Reitz GGX
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*/
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static float NormalDistribution_GGX(const Vector3 &n, const Vector3 &h, float roughness) {
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const float a = roughness * roughness;
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const float a2 = a * a;
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const float dot{Vector3::Dot(n, h)};
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const float div{dot * dot * (a2 - 1) + 1};
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return a2 / (M_PI * div * div);
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}
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/**
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* \brief BRDF Geometry Function >> Schlick GGX (Direct Lighting + UE4 implementation - squared(roughness))
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* \param n Normal of the surface
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* \param v Normalized view direction
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* \param roughness Roughness of the material
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* \return BRDF Geometry Term using SchlickGGX
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*/
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static float GeometryFunction_SchlickGGX(const Vector3 &n, const Vector3 &v, float roughness) {
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float cosAngle{ Vector3::Dot(n,v) };
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float k{ (roughness + 1) * (roughness + 1) / 8 };
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return {cosAngle / (cosAngle * (1 - k) + k) };
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}
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/**
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* \brief BRDF Geometry Function >> Smith (Direct Lighting)
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* \param n Normal of the surface
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* \param v Normalized view direction
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* \param l Normalized light direction
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* \param roughness Roughness of the material
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* \return BRDF Geometry Term using Smith (> SchlickGGX(n,v,roughness) * SchlickGGX(n,l,roughness))
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*/
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static float GeometryFunction_Smith(const Vector3 &n, const Vector3 &v, const Vector3 &l, float roughness) {
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return { GeometryFunction_SchlickGGX(n,v,roughness) * GeometryFunction_SchlickGGX(n,l,roughness) };
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}
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}
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} |