Function nalgebra_glm::refract_vec

pub fn refract_vec<N: Real, D: Dimension>(
    i: &TVec<N, D>, 
    n: &TVec<N, D>, 
    eta: N
) -> TVec<N, D> where
    DefaultAllocator: Alloc<N, D>, 

For the incident vector i and surface normal n, and the ratio of indices of refraction eta, return the refraction vector.