void CAngularSpectralProperties::calculateAngularProperties(
std::shared_ptr<CSpectralSample> const & t_SpectralSample, MaterialType const t_Type)
{
assert(t_SpectralSample != nullptr);
auto aMeasuredData = t_SpectralSample->getMeasuredData();
if(m_Angle != 0)
{
auto aSourceData = t_SpectralSample->getSourceData();
auto aWavelengths = aMeasuredData->getWavelengths();
auto aT = aMeasuredData->properties(SampleData::T);
assert(aT->size() == aWavelengths.size());
auto aRf = aMeasuredData->properties(SampleData::Rf);
assert(aRf->size() == aWavelengths.size());
auto aRb = aMeasuredData->properties(SampleData::Rb);
assert(aRb->size() == aWavelengths.size());
auto lowLambda = 0.3;
auto highLambda = 2.5;
// TODO: Only one side is measured and it is considered that front properties are equal
// to back properties
auto aTSolNorm =
t_SpectralSample->getProperty(lowLambda, highLambda, Property::T, Side::Front);
for(size_t i = 0; i < aWavelengths.size(); ++i)
{
auto ww = aWavelengths[i] * 1e-6;
auto T = (*aT)[i].value();
auto Rf = (*aRf)[i].value();
auto Rb = (*aRb)[i].value();
auto aSurfaceType = coatingType.at(t_Type);
auto aFrontFactory = CAngularPropertiesFactory(T, Rf, m_Thickness, aTSolNorm);
auto aBackFactory = CAngularPropertiesFactory(T, Rb, m_Thickness, aTSolNorm);
auto aFrontProperties = aFrontFactory.getAngularProperties(aSurfaceType);
auto aBackProperties = aBackFactory.getAngularProperties(aSurfaceType);
auto Tangle = aFrontProperties->transmittance(m_Angle, ww);
auto Rfangle = aFrontProperties->reflectance(m_Angle, ww);
auto Rbangle = aBackProperties->reflectance(m_Angle, ww);
m_AngularData->addRecord(ww * 1e6, Tangle, Rfangle, Rbangle);
}
}
else
{
m_AngularData = aMeasuredData;
}
}
bool Tracer::scatterRefractive(const IntersectDescr& node, Ray& ray) const
{
// here we throw the dice to dices whether to reflect or to refract
const double probability = ::uniform_distrib_( ::rand_gen_ );
// heuristic to determine material transition
// note, this assumes that only one type of refractive material exists AND
// that two objects do not intersect, such that an interface within a
// non-air material exists (well, its not that strict, but simpler to
// explain this way)
const double surface_dot = node.normal_.dot( node.incident_ );
const bool is_entry = ( surface_dot <= 0. );
// 1.52 is for crown glass
const double refractive_idx_from = is_entry ? 1.0 : 1.52;
const double refractive_idx_to = is_entry ? 1.52 : 1.0;
// The reflectance and refract functions require the normal to point into
// the direction of the first material. If this is not the case, we invert
// its direction.
const Vector corrected_normal = is_entry ? node.normal_ : -1. * node.normal_;
const double reflect = reflectance(
corrected_normal, node.incident_, refractive_idx_from, refractive_idx_to );
if( probability <= reflect )
{
return scatterSpecular( node, ray );
}
else
{
Vector refracted_dir = refract( corrected_normal,
node.incident_,
refractive_idx_from,
refractive_idx_to );
if( refracted_dir.length() > 1e-4 )
{
ray = Ray{ node.point_, refracted_dir.normalized() };
return true;
}
else
{
return false;
}
}
return false; // should never get here, though
}
a3Spectrum a3Dieletric::sample(const t3Vector3f& wi, t3Vector3f& wo, float* pdf, const a3Intersection& its) const
{
static a3Random random;
t3Vector3f n = its.getNormal();
// 入射光 / 出射光所在折射率
float etai = 1.0f, etat = its.shape->refractiveIndex;
// 光密到光疏
if(wi.dot(n) > 0)
{
t3Math::swap(etai, etat);
// 翻转法线 保持与入射光线一个平面
n = -n;
}
float eta = etai / etat;
// 菲涅尔反射(反射的概率)
//float Fr = a3FresnelDielectric(costhetai, costhetat, etai, etat);
float Fr = reflectance(n, wi, etai, etat);
//float P = 0.25 + 0.5 * Fr;
float r = random.randomFloat();
if(r > Fr)
{
bool TIR = false;
wo = refract(n, wi, etai, etat, TIR);
*pdf = 1.0f;
eta = 1 / eta;
return getColor(its) * specularTransmittance / t3Math::Abs(wo.dot(n));
}
else
{
wo = reflect(n, wi);
*pdf = 1.0f;
// 镜面反射
return getColor(its) * specularReflectance / t3Math::Abs(wo.dot(n));
}
}
