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bevy_math: faster sphere sampling (#14168)

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Uses fewer transcendental functions than the existing approach
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ickk 2024-07-16 01:01:18 +10:00 committed by GitHub
parent da997dd0ea
commit 3dd4953b97
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1 changed files with 15 additions and 15 deletions
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30
crates/bevy_math/src/sampling/shape_sampling.rs
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@ -164,30 +164,30 @@ impl ShapeSample for Circle {
} }
} }
/// Boundary sampling for unit-spheres
#[inline]
fn sample_unit_sphere_boundary<R: Rng + ?Sized>(rng: &mut R) -> Vec3 {
let z = rng.gen_range(-1f32..=1f32);
let (a_sin, a_cos) = rng.gen_range(-PI..=PI).sin_cos();
let c = (1f32 - z * z).sqrt();
let x = a_sin * c;
let y = a_cos * c;
Vec3::new(x, y, z)
}
impl ShapeSample for Sphere { impl ShapeSample for Sphere {
type Output = Vec3; type Output = Vec3;
fn sample_interior<R: Rng + ?Sized>(&self, rng: &mut R) -> Vec3 { fn sample_interior<R: Rng + ?Sized>(&self, rng: &mut R) -> Vec3 {
// https://mathworld.wolfram.com/SpherePointPicking.html
let theta = rng.gen_range(0.0..TAU);
let phi = rng.gen_range(-1.0_f32..1.0).acos();
let r_cubed = rng.gen_range(0.0..=(self.radius * self.radius * self.radius)); let r_cubed = rng.gen_range(0.0..=(self.radius * self.radius * self.radius));
let r = r_cubed.cbrt(); let r = r_cubed.cbrt();
Vec3 {
x: r * phi.sin() * theta.cos(), r * sample_unit_sphere_boundary(rng)
y: r * phi.sin() * theta.sin(),
z: r * phi.cos(),
}
} }
fn sample_boundary<R: Rng + ?Sized>(&self, rng: &mut R) -> Vec3 { fn sample_boundary<R: Rng + ?Sized>(&self, rng: &mut R) -> Vec3 {
let theta = rng.gen_range(0.0..TAU); self.radius * sample_unit_sphere_boundary(rng)
let phi = rng.gen_range(-1.0_f32..1.0).acos();
Vec3 {
x: self.radius * phi.sin() * theta.cos(),
y: self.radius * phi.sin() * theta.sin(),
z: self.radius * phi.cos(),
}
} }
} }