Function antler::colour

pub(crate) fn colour(
    input: &Input<'_>, 
    camera: &Camera, 
    ray: &mut Ray, 
    weight: f64, 
    pixel: [usize; 2], 
    data: &mut Output, 
    rng: &mut ThreadRng, 
    norm: &Unit<Vector3<f64>>, 
    grad: &Gradient<LinSrgba>, 
    abs_frac: f64
) -> f64

Determine the colour of a ray-surface collision. Record the data.