material.rs

use std::num::zero;
use std::rand::Rng;
use std::rand::distributions::range::SampleRange;

use vecmath::vector::Vec3;
use vecmath::ray::Ray;

use lightray::Lightray;
use objecthit::ObjectHit;

pub trait Material<T> {
    fn reflect<R: Rng>(&self, lray: &Lightray<T>, ohit: &ObjectHit<T>, r: &mut R) -> Lightray<T>;
    
    fn has_emission(&self) -> bool;
    fn emission(&self, wavelength: f32) -> f32;
}

pub struct Clay;
    
impl<T: Num + FloatMath + PartialOrd + SampleRange> Material<T> for Clay {
    fn reflect<R: Rng>(&self, lray: &Lightray<T>, ohit: &ObjectHit<T>, rng: &mut R) -> Lightray<T> {
        let new_dir = Vec3::cos_hemisphere(rng).align(
            &if lray.ray.dir.dotv(&ohit.hit.normal) < zero() { ohit.hit.normal } else { ohit.hit.normal.cflip() }
        );
        Lightray::new(Ray::new(ohit.hit.pos, new_dir), lray.wavelength, 1f32)
    }
    fn has_emission(&self) -> bool { false }
    fn emission(&self, wavelength: f32) -> f32 { 0.0f32 }
}