src/rcrt/lights/SphericalLight.cpp

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#include "SphericalLight.h"

namespace rcrt
{

SphericalLight::SphericalLight(const RGBColor& power, const float& rad, const Point3D& c, const int& samp):
        Light(power, samp),radius(rad),center(c), radius2(rad*rad)
{
        
}

SphericalLight::~SphericalLight()
{
}


LightSample SphericalLight::illuminate(const Point3D& p, const Vec3D& normal) const
{
        Vec3D dir = center - p;
        float distSqr = dir * dir;
        if(distSqr <= radius2)
        {
                return LightSample(0,0,0,0);
        }
        float dist = sqrt(distSqr);
        float idistSqr = 1.f/(distSqr);
        float cosAlpha = std::sqrt(1.f - radius2 * idistSqr);
        dir = dir * 1.f/dist;
        Vec3D du, dv;
        dir.getCS(du, dv);
        const float xi1 = float(rand()) / float(RAND_MAX);
        const float xi2 = float(rand()) / float(RAND_MAX);
        double cosAng = 1.0 - (1.0-(double)cosAlpha) * xi2;
        double sinAng = sqrt(1.0 - cosAng*cosAng);
        float t1 = 2.0*M_PI*xi1;
        Vec3D sampleDir((du*cos(t1) + dv*sin(t1))*sinAng + dir*cosAng); 
                
        const Vec3D vf = p - center;
        const float ea = sampleDir * sampleDir;
        const float eb = 2.0*vf*sampleDir;
        const float ec = vf*vf-radius2+0.00001f;
        const float osc = eb*eb-4.0*ea*ec;
        float d1;
        if(osc < 0) {
                d1 = sqrt(ec/ea);
        } else {
                d1 = (-eb-sqrt(osc))/(2.0*ea);
        }
        
        return LightSample(2.f * (1.f - cosAlpha), sampleDir, d1, power);
}

void SphericalLight::illuminate(const Point3D& p, const Vec3D& normal, std::vector<LightSample>& samples,
                        const int& noSamples, Scene* s) const
{
        Vec3D dir(center-p);
        const float dist2 = dir * dir;
        if(dist2 < radius2)
                return;
        const float cosThetaMax(sqrt(std::max(0.0f, 1.0f - radius2 / (dist2  * 0.01f + float(sqrt(dist2)) * 0.25f + 1))));
        const float scale(2.0f * M_PI * (1.0f - cosThetaMax));
        const float weight(scale / noSamples);
        for(int i = 0; i < noSamples; i++){
                samples.push_back(illuminate(p, normal));
                samples.back().setWeight(weight);
        }
}

RGBColor SphericalLight::getEmitted(const Vec3D& dir, const Point3D& pos) const
{
        return power;
}

void SphericalLight::emitPhoton(Photon* photon) const
{
        //TODO
}

}

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