public float Evaluate(float cosi)
{
cosi = LR.Clamp(cosi, -1.0f, 1.0f);
// Compute indices of refraction for dielectric
bool entering = cosi > 0.0;//>0 入射
float ei = eta_i, et = eta_t;
if (!entering)
{
LR.Swap(ei, et);
}
// Compute _sint_ using Snell's law
float sint = ei / et * (float)Math.Sqrt(Math.Max(0.0f, 1.0f - cosi * cosi));//处理溢出？
if (sint >= 1.0)
{
// Handle total internal reflection
return(1.0f);
}
else
{
float cost = (float)Math.Sqrt(Math.Max(0.0f, 1.0f - sint * sint));
return(BSDFFunction.FrDiel(Math.Abs(cosi), cost, ei, et));
}
}
public static float SinPhi(Vector w)
{
float sintheta = SinTheta(w);
if (sintheta == 0.0f)
{
return(0.0f);
}
return(LR.Clamp(w.y / sintheta, -1.0f, 1.0f));
}
public static float CosPhi(Vector w)
{
float sintheta = SinTheta(w);
if (sintheta == 0.0f)
{
return(1.0f); //垂直
}
return(LR.Clamp(w.x / sintheta, -1.0f, 1.0f));
}