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use std::sync::Arc;
use crate::{hittable::{HitRecord, Hittable, AABB}, material::{Isotropic, Material}, ray::Ray, texture::Texture, vec3::{Vec3, Point3}};
pub struct ConstantMedium {
boundary: Arc<dyn Hittable>,
phase_function: Arc<dyn Material>,
neg_inv_density: f64,
}
impl ConstantMedium {
pub fn new(boundary: Arc<dyn Hittable>, density: f64, texture: Arc<dyn Texture>) -> Self {
Self {
boundary,
phase_function: Arc::new(Isotropic::from_texture(texture)),
neg_inv_density: -1.0/density,
}
}
}
impl Hittable for ConstantMedium {
// TODO: this only support convex shapes.
fn hit(&self, ray: &Ray, t_min: f64, t_max: f64) -> Option<HitRecord> {
let mut record_1 = self.boundary.hit(ray, -f64::INFINITY, f64::INFINITY)?;
let mut record_2 = self.boundary.hit(ray, record_1.t + 0.0001, f64::INFINITY)?;
if record_1.t < t_min {
record_1.t = t_min;
}
if record_2.t > t_max {
record_2.t = t_max;
}
if record_1.t >= record_2.t {
return None;
}
if record_1.t < 0.0 {
record_1.t = 0.0;
}
let ray_length = ray.direction.length();
let distance_inside_boundary = (record_2.t - record_1.t) * ray_length;
let hit_distance = self.neg_inv_density * rand::random::<f64>().ln();
if hit_distance > distance_inside_boundary {
return None;
}
let t = record_1.t + hit_distance / ray_length;
Some(HitRecord {
p: ray.at(t),
t,
material: Some(self.phase_function.clone()),
normal: Vec3 { x: 1.0, y: 0.0, z: 0.0 }, // arbitrary
front_face: true, // arbitrary
u: 0.0, // arbitrary
v: 0.0, // arbitrary
})
}
fn bounding_box(&self, time_start: f64, time_end: f64) -> Option<AABB> {
self.boundary.bounding_box(time_start, time_end)
}
}
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