60 lines
2.4 KiB
C++
60 lines
2.4 KiB
C++
#include "light/light.h"
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#include "scene/scene.h"
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#include "shader/cooktorranceshader.h"
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CookTorranceShader::CookTorranceShader(Color const &diffCol, Color const &ctCol, float IOR, float roughness,
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float diffCoeff, float ctCoeff) : diffuseColor(diffCol * diffCoeff),
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ctColor(ctCol * ctCoeff), F0(IOR),
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m(roughness) {}
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float CookTorranceShader::D(float NdotH) const {
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// Beckmann distribution
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float const r2 = m * m;
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float const NdotH2 = NdotH * NdotH;
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return expf((NdotH2 - 1.0f) / (r2 * NdotH2)) / (4.0f * r2 * powf(NdotH, 4.0f));
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}
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float CookTorranceShader::F(float VdotH) const {
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// Schlicks approximation
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return F0 + (1.0f - F0) * powf(1.0f - VdotH, 5);
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}
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float CookTorranceShader::G(float NdotH, float NdotV, float VdotH, float NdotL) const {
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return std::min(1.0f, std::min(
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2.0f * NdotH * NdotV / VdotH, 2.0f * NdotH * NdotL / VdotH));
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}
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Color CookTorranceShader::shade(Scene const &scene, Ray const &ray) const {
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Color fragmentColor;
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if (m >= 0.0f) {
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// Accumulate the light over all light sources
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for (const auto &light: scene.lights()) {
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Light::Illumination illum;
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illum = light->illuminate(scene, ray);
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float const NdotL = std::max(0.0f, dotProduct(-illum.direction, ray.normal));
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if (NdotL <= 0.0f)
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continue;
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// Diffuse term
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Color const diffuse = this->diffuseColor / float(PI);
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fragmentColor += diffuse * NdotL * illum.color;
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// Cook-Torrance term
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// half angle vector
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Vector3d const H = normalized(-illum.direction - ray.direction);
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float const NdotH = std::max(0.0f, dotProduct(ray.normal, H));
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float const NdotV = std::max(0.0f, dotProduct(ray.normal, -ray.direction));
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float const VdotH = std::max(0.0f, dotProduct(-ray.direction, H));
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if (NdotV * NdotL > EPSILON) {
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Color const specular = this->ctColor * (F(VdotH) * D(NdotH) * G(NdotH, NdotV, VdotH, NdotL)) /
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(float(PI) * NdotV * NdotL);
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fragmentColor += specular * NdotL * illum.color;
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}
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}
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}
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return fragmentColor;
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}
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