float mReflectCoeff; //!< Fresnel reflection coefficient (for glass)
Bsdf(
Ray aRay,
ref Normal normal,
Material Material,
SceneGeometryInfo aScene)
{
Setup(aRay, ref normal, Material, aScene);
}
void Setup(
Ray aRay,
ref Normal normal,
Material Material,
SceneGeometryInfo aScene)
{
mMaterialID = -1;
mFrame.SetFromZ(ref normal);
var invdir = -aRay.Direction;
mLocalDirFix = mFrame.ToLocal(ref invdir);
// reject rays that are too parallel with tangent plane
if (Math.Abs(mLocalDirFix.z) < Consts.EPS_COSINE)
{
return;
}
GetComponentProbabilities(Material, mProbabilities);
mIsDelta = (Math.Abs(mProbabilities.diffProb) < MathLab.Epsilon) && (Math.Abs(mProbabilities.phongProb) < MathLab.Epsilon);
// now it becomes valid
mMaterialID = 1;//Material.mIOR;
}
float AlbedoRefract(Material aMaterial)
{
return 1f;
}
float AlbedoReflect(Material aMaterial)
{
return Luminance(aMaterial.mMirrorReflectance);
}
float AlbedoPhong(Material aMaterial)
{
return Luminance(aMaterial.mPhongReflectance);
}
float AlbedoDiffuse(Material aMaterial)
{
return Luminance(aMaterial.mDiffuseReflectance);
}
void GetComponentProbabilities(
Material aMaterial,
ComponentProbabilities oProbabilities)
{
mReflectCoeff = Utils.FresnelDielectric(mLocalDirFix.z, aMaterial.mIOR);
float albedoDiffuse = AlbedoDiffuse(aMaterial);
float albedoPhong = AlbedoPhong(aMaterial);
float albedoReflect = mReflectCoeff * AlbedoReflect(aMaterial);
float albedoRefract = (1f - mReflectCoeff) * AlbedoRefract(aMaterial);
float totalAlbedo = albedoDiffuse + albedoPhong + albedoReflect + albedoRefract;
if (totalAlbedo < 1e-9f)
{
oProbabilities.diffProb = 0f;
oProbabilities.phongProb = 0f;
oProbabilities.reflProb = 0f;
oProbabilities.refrProb = 0f;
mContinuationProb = 0f;
}
else
{
oProbabilities.diffProb = albedoDiffuse / totalAlbedo;
oProbabilities.phongProb = albedoPhong / totalAlbedo;
oProbabilities.reflProb = albedoReflect / totalAlbedo;
oProbabilities.refrProb = albedoRefract / totalAlbedo;
// The continuation probability is max component from reflectance.
// That way the weight of sample will never rise.
// Luminance is another very valid option.
mContinuationProb =
(aMaterial.mDiffuseReflectance +
aMaterial.mPhongReflectance +
mReflectCoeff * aMaterial.mMirrorReflectance).Max() +
(1f - mReflectCoeff);
mContinuationProb = Math.Min(1f, Math.Max(0f, mContinuationProb));
}
}
