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use crate::{
material::Material,
ray::Ray,
util::random_double,
vec3::{dot, reflect, refract, Color},
};
pub struct Dialectric {
refraction_index: f64,
}
impl Dialectric {
pub fn new(refraction_index: f64) -> Self {
Self { refraction_index }
}
fn reflectance(cosine: f64, refraction_index: f64) -> f64 {
// Schlick approximation
let mut r0 = (1.0 - refraction_index) / (1.0 + refraction_index);
r0 = r0 * r0;
r0 + (1.0 - r0) * (1.0 - cosine).powf(5.0)
}
}
impl Material for Dialectric {
fn scatter(
&self,
ray: &crate::ray::Ray,
rec: &crate::geometry::HitRecord,
) -> Option<(Ray, Color)> {
let refraction_ratio = if rec.front_face {
1.0 / self.refraction_index
} else {
self.refraction_index
};
let unit_direction = &ray.direction().unit_vector();
let cos_theta = f64::min(dot(&-unit_direction, &rec.normal), 1.0);
let sin_theta = f64::sqrt(1.0 - cos_theta * cos_theta);
let cannot_refract = refraction_ratio * sin_theta > 1.0;
let direction = if cannot_refract
|| Dialectric::reflectance(cos_theta, refraction_ratio) > random_double()
{
reflect(unit_direction, &rec.normal)
} else {
refract(unit_direction, &rec.normal, refraction_ratio)
};
Some((Ray::new(rec.point, direction), Color::new(1.0, 1.0, 1.0)))
}
}
|
