| // Copyright 2019 Developers of the Rand project. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| use num_traits::Float; |
| use crate::{uniform::SampleUniform, Distribution, Uniform}; |
| use rand::Rng; |
| |
| /// Samples uniformly from the unit ball (surface and interior) in three |
| /// dimensions. |
| /// |
| /// Implemented via rejection sampling. |
| /// |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use rand_distr::{UnitBall, Distribution}; |
| /// |
| /// let v: [f64; 3] = UnitBall.sample(&mut rand::thread_rng()); |
| /// println!("{:?} is from the unit ball.", v) |
| /// ``` |
| #[derive(Clone, Copy, Debug)] |
| pub struct UnitBall; |
| |
| impl<F: Float + SampleUniform> Distribution<[F; 3]> for UnitBall { |
| #[inline] |
| fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> [F; 3] { |
| let uniform = Uniform::new(F::from(-1.).unwrap(), F::from(1.).unwrap()); |
| let mut x1; |
| let mut x2; |
| let mut x3; |
| loop { |
| x1 = uniform.sample(rng); |
| x2 = uniform.sample(rng); |
| x3 = uniform.sample(rng); |
| if x1 * x1 + x2 * x2 + x3 * x3 <= F::from(1.).unwrap() { |
| break; |
| } |
| } |
| [x1, x2, x3] |
| } |
| } |