@absulit/points/build/core/random.js

A Generative Art library made in WebGPU

/* @ts-self-types="./random.d.ts" */
/**
 * Various random functions.
 *
 * These are wgsl functions, not js functions.
 * The function is enclosed in a js string constant,
 * to be appended into the code to reference it in the string shader.
 * @module points/random
 */

/**
 * Single random number.
 * Use `seed` to change seed.
 * @type {String}
 * @return {f32}
 *
 * @example
 * // js
 * import { random } from 'points/random';
 *
 * // wgsl string
 * ${random}
 * let value = random();
 *
 */
const random = /*wgsl*/`

var<private> a:i32 = 1664525;
var<private> c:i32 = 1013904223;
var<private> m = pow(2, 32);
var<private> seed:i32 = 958736;

fn nextRand() -> i32 {
    seed = (a * seed + c) % i32(m);
    return seed;
}

fn random() -> f32 {
    return f32(nextRand()) / f32(m) / .5;
}

`;

/**
 * Random number that returns a `vec2f`.<br>
 * You have to set the `rand_seed` before calling `rand()`.
 * @type {String}
 * @return {f32} equivalent to `rand_seed.y` and `rand_seed` is the result.
 *
 * @example
 * // js
 * import { rand } from 'points/random';
 * rand_seed.x = .01835255;
 *
 * // wgsl string
 * ${rand}
 * let value = rand();
 */
const rand = /*wgsl*/`
var<private> rand_seed : vec2f;

fn rand() -> f32 {
    rand_seed.x = fract(cos(dot(rand_seed, vec2f(23.14077926, 232.61690225))) * 136.8168);
    rand_seed.y = fract(cos(dot(rand_seed, vec2f(54.47856553, 345.84153136))) * 534.7645);
    return rand_seed.y;
}
`;

/**
 * Random number from `vec2f` param
 * @type {String}
 * @param {vec2f} co `vec2f` vector
 * @returns {f32}
 *
 * @example
 * // js
 * import { rand2 } from 'points/random';
 *
 * // wgsl string
 * ${rand2}
 * let value = rand2(uvr);
 */
const rand2 = /*wgsl*/`
fn rand2(co: vec2f) -> f32 {
    return fract(sin(dot(co, vec2(12.9898, 78.233))) * 43758.5453);
}
`;

export { rand, rand2, random };