public static XMVector RefractV(XMVector incident, XMVector normal, XMVector refractionIndex)
{
//// Result = RefractionIndex * Incident - Normal * (RefractionIndex * dot(Incident, Normal) +
//// sqrt(1 - RefractionIndex * RefractionIndex * (1 - dot(Incident, Normal) * dot(Incident, Normal))))
XMVector zero = XMVector.Zero;
XMVector incidentDotNormal = XMVector4.Dot(incident, normal);
// R = 1.0f - RefractionIndex * RefractionIndex * (1.0f - IDotN * IDotN)
XMVector r = XMVector.NegativeMultiplySubtract(incidentDotNormal, incidentDotNormal, XMGlobalConstants.One);
r = XMVector.Multiply(r, refractionIndex);
r = XMVector.NegativeMultiplySubtract(r, refractionIndex, XMGlobalConstants.One);
if (XMVector4.LessOrEqual(r, zero))
{
// Total internal reflection
return(zero);
}
else
{
// R = RefractionIndex * IDotN + sqrt(R)
r = r.Sqrt();
r = XMVector.MultiplyAdd(refractionIndex, incidentDotNormal, r);
// Result = RefractionIndex * Incident - Normal * R
XMVector result = XMVector.Multiply(refractionIndex, incident);
result = XMVector.NegativeMultiplySubtract(normal, r, result);
return(result);
}
}
public static bool LessOrEqual(XMVector c1, XMVector c2)
{
return(XMVector4.LessOrEqual(c1, c2));
}
