voronoi2.ts

// SPDX-License-Identifier: Apache-2.0
import type { FloatSym, Vec2Sym, Vec3Sym } from "@thi.ng/shader-ast";
import { F, V2 } from "@thi.ng/shader-ast/api/types";
import { forLoop } from "@thi.ng/shader-ast/ast/controlflow";
import { defn, ret } from "@thi.ng/shader-ast/ast/function";
import {
	FLOAT0,
	SQRT2,
	float,
	int,
	vec2,
	vec3,
} from "@thi.ng/shader-ast/ast/lit";
import {
	add,
	addSelf,
	div,
	inc,
	lte,
	mul,
	sub,
} from "@thi.ng/shader-ast/ast/ops";
import { $xy, $z } from "@thi.ng/shader-ast/ast/swizzle";
import { sym } from "@thi.ng/shader-ast/ast/sym";
import {
	dot,
	floor,
	fract,
	pow,
	smoothstep,
	sqrt,
} from "@thi.ng/shader-ast/builtin/math";
import { hash32 } from "./hash.js";

/**
 * IQ's parametric 2D voronoise. Depending on `u` and `v`, this function
 * produces 4 different noise types
 *
 * - cell noise `(0,0)`
 * - voronoi `(1,0)`
 * - perlin noise `(0,1)`
 * - voronoise `(1,1)`
 *
 * http://www.iquilezles.org/www/articles/voronoise/voronoise.htm
 *
 * Note: This implementation uses the improved {@link hash32} by Dave Hoskins
 * instead of iq's original {@link hash3}.
 *
 * @param p -
 * @param u -
 * @param v -
 */
export const voronoise2 = defn(F, "voronoise2", [V2, F, F], (x, u, v) => {
	let p: Vec2Sym;
	let f: Vec2Sym;
	let coeff: Vec3Sym;
	let k: FloatSym;
	let va: FloatSym;
	let wt: FloatSym;
	let g: Vec2Sym;
	let o: Vec3Sym;
	let r: Vec2Sym;
	let w: FloatSym;
	return [
		(p = sym(floor(x))),
		(f = sym(fract(x))),
		(coeff = sym(vec3(u, u, 1))),
		(k = sym(add(1, mul(63, pow(sub(1, v), float(4)))))),
		(va = sym(FLOAT0)),
		(wt = sym(FLOAT0)),
		forLoop(
			sym(int(-2)),
			(i) => lte(i, int(2)),
			inc,
			(i) => [
				forLoop(
					sym(int(-2)),
					(j) => lte(j, int(2)),
					inc,
					(j) => [
						(g = sym(vec2(float(i), float(j)))),
						(o = sym(mul(hash32(add(p, g)), coeff))),
						(r = sym(add(sub(g, f), $xy(o)))),
						(w = sym(
							pow(
								sub(
									1,
									smoothstep(FLOAT0, SQRT2, sqrt(dot(r, r)))
								),
								k
							)
						)),
						addSelf(va, mul(w, $z(o))),
						addSelf(wt, w),
					]
				),
			]
		),
		ret(div(va, wt)),
	];
});