src/rcrt/bxdf/fresnel.hpp

Go to the documentation of this file.

#ifndef FRESNEL_H_
#define FRESNEL_H_

#include <complex>

namespace rcrt
{

inline float fresnelTerm(float c, std::complex<float> n)
{
        std::complex<float> g2 = n*n + c*c - 1.0f;
        float absg2 = abs(g2);//sqrt(g2.real()*g2.real() + g2.imag()*g2.imag());
        float a = sqrt((absg2 + g2.real())/2.0f);
        float b = sqrt((absg2 - g2.real())/2.0f);
        float st = (1.0f-c*c)/c;
        float b2 = b * b;
        return 0.5*((a-c)*(a-c)+b2)/((a+c)*(a+c)+b2)*
                (1.0+((a-st)*(a-st)+b2)/((a+st)*(a+st)+b2));
}

inline Vec3D snell(const Vec3D& wInc, const Vec3D& normal, const float& eta)
{
        float cosI = wInc * normal;
        float cosT = 1.0 - (eta * eta) * (1.0 - cosI * cosI);
                                
        if (cosT <= 0.0f) {//total internal reflection
                return wInc.reflect(normal);
        }
                                
        cosT = eta * cosI + sqrt(cosT);

        return wInc * eta + normal * -cosT;
}

inline float frRDielectric(const float& cosI, const float& cosT,
                const float& etaI, const float& etaT)
{
        const float Rp = ((etaI * cosT) - (etaT * cosI)) / ((etaI * cosT) + (etaT * cosI));
        const float Rs = ((etaI * cosI) - (etaT * cosT)) / ((etaI * cosI) + (etaT * cosT));
        return (Rp*Rp + Rs*Rs) / 2.0f;
}

inline float frTDielectric(const float& cosI, const float& cosT,
                const float& etaI, const float& etaT)
{
        return 1-frRDielectric(cosI,cosT,etaI,etaT);
}


}

#endif /*FRESNEL_H_*/

---