worlds-history-sim-rs/planet/src/math_util.rs

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2022-09-19 10:54:10 +02:00
use {
bevy::math::Vec3A,
rand::{rngs::StdRng, Rng},
std::{
error::Error,
f32::consts::{PI, TAU},
fmt::{Debug, Display},
},
};
#[derive(Debug, Copy, Clone)]
pub enum CartesianError {
InvalidAlpha(f32),
}
impl Error for CartesianError {
fn source(&self) -> Option<&(dyn Error + 'static)> {
None
}
fn description(&self) -> &str {
"description() is deprecated; use Display"
}
fn cause(&self) -> Option<&dyn Error> {
self.source()
}
}
impl Display for CartesianError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
CartesianError::InvalidAlpha(alpha) => {
f.write_fmt(format_args!("Alpha value must be [0..PI], was {}", alpha))
2022-09-19 10:54:10 +02:00
},
}
}
}
pub fn cartesian_coordinates(
alpha: f32,
mut beta: f32,
radius: f32,
) -> Result<Vec3A, CartesianError> {
if alpha < 0.0 || alpha > PI {
return Err(CartesianError::InvalidAlpha(alpha));
}
if beta < 0.0 {
while beta < 0.0 {
beta += PI;
}
} else {
beta = beta.repeat(TAU);
}
let sin_alpha = f32::sin(alpha);
Ok(Vec3A::new(
sin_alpha * f32::cos(beta) * radius,
f32::cos(alpha) * radius,
sin_alpha * f32::sin(beta) * radius,
))
}
pub fn random_point_in_sphere(rng: &mut StdRng, radius: f32) -> Vec3A {
// https://karthikkaranth.me/blog/generating-random-points-in-a-sphere/#better-choice-of-spherical-coordinates
let u = rng.gen_range(0.0..1.0);
let v = rng.gen_range(0.0..1.0);
let theta = u * TAU;
let phi = f32::acos(2.0 * v - 1.0);
let r = f32::cbrt(rng.gen_range(0.0..radius));
let sin_theta = f32::sin(theta);
let cos_theta = f32::cos(theta);
let sin_phi = f32::sin(phi);
let cos_phi = f32::cos(phi);
Vec3A::new(
r * sin_phi * cos_theta,
r * sin_phi * sin_theta,
r * cos_phi,
)
}
pub fn mix_values(a: f32, b: f32, weight_b: f32) -> f32 {
(b * weight_b) + (a * (1.0 - weight_b))
}
pub trait RepeatNum {
fn repeat(self, length: Self) -> Self;
}
impl RepeatNum for f32 {
fn repeat(self, length: f32) -> f32 {
f32::clamp(self - (self / length).floor() * length, 0.0, length)
}
}