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//! Implements sphere
//!
//! Spheres are relatively easy to calculate intersections between
use crate::{Float, NEAR_ZERO};
use crate::core::{Ray, Vector3f, Bound3f};
use crate::world::{Hittable, DynHittable, Intersection, Instancable};
pub struct Sphere {
radius: Float,
}
impl Sphere {
pub fn new(radius: Float) -> Sphere {
Sphere {
radius,
}
}
fn norm_at(&self, point: &Vector3f) -> Vector3f {
*point / self.radius
}
}
impl Hittable for Sphere {
// Implementation from ray tracing in a weekend
fn intersect(&self, ray: &Ray) -> Option<Intersection> {
let a = ray.direction.len_squared();
let half_b = ray.origin.dot(&ray.direction);
let c = ray.origin.len_squared() - self.radius * self.radius;
let disc = half_b*half_b - a*c;
if disc < 0.0 {
None
} else {
let disc_sqrt = disc.sqrt();
let mut distance = -half_b - disc_sqrt;
if distance <= NEAR_ZERO {
distance = -half_b + disc_sqrt;
}
if distance <= NEAR_ZERO {
return None;
}
distance /= a;
let w = ray.at(distance);
Some(Intersection::new(
self.norm_at(&w),
w,
ray,
distance,
))
}
}
/// Box containing the circle
///
/// # Examples
///
/// ```
/// use rendering::core::Vector3f;
/// use rendering::world::{Hittable, shapes::Sphere};
///
/// let sph = Sphere::new(1.0);
/// let b = sph.bounding_box();
///
/// assert!(b.min.x == -1.0 && b.min.y == -1.0 && b.min.z == -1.0);
/// assert!(b.max.x == 1.0 && b.max.y == 1.0 && b.max.z == 1.0);
/// ```
fn bounding_box(&self) -> Bound3f {
let offset = Vector3f::new(self.radius);
Bound3f::new(-offset, offset)
}
}
impl Instancable for Sphere {}
impl Into<DynHittable> for Sphere {
fn into(self) -> DynHittable {
DynHittable::new(Box::new(self))
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn sphere_intersect() {
let sph = Sphere::new(2.0);
let ray = Ray {
origin: Vector3f::new_xyz(1.0, 0.0, 0.0),
direction: Vector3f::new_xyz(0.0, 1.0, 1.5).norm(),
};
let dist = sph.intersect(&ray).unwrap();
assert!((dist.t - 1.732).abs() < 0.01);
}
}
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