curl3.ts

// SPDX-License-Identifier: Apache-2.0
import type { Vec2Sym, Vec3Sym } from "@thi.ng/shader-ast";
import { F, V3 } from "@thi.ng/shader-ast/api/types";
import { defn, ret } from "@thi.ng/shader-ast/ast/function";
import { vec2, vec3 } from "@thi.ng/shader-ast/ast/lit";
import { add, div, mul, sub } from "@thi.ng/shader-ast/ast/ops";
import { $, $x, $y, $z } from "@thi.ng/shader-ast/ast/swizzle";
import { sym } from "@thi.ng/shader-ast/ast/sym";
import { snoiseVec3 } from "./simplex3.js";

export const curlNoise3 = defn(V3, "curlNoise3", [V3, F], (p, e) => {
	let D: Vec2Sym;
	let px0: Vec3Sym;
	let px1: Vec3Sym;
	let py0: Vec3Sym;
	let py1: Vec3Sym;
	let pz0: Vec3Sym;
	let pz1: Vec3Sym;
	return [
		(D = sym(vec2(e, 0))),
		(px0 = sym(snoiseVec3(sub(p, $(D, "xyy"))))),
		(px1 = sym(snoiseVec3(add(p, $(D, "xyy"))))),
		(py0 = sym(snoiseVec3(sub(p, $(D, "yxy"))))),
		(py1 = sym(snoiseVec3(add(p, $(D, "yxy"))))),
		(pz0 = sym(snoiseVec3(sub(p, $(D, "yyx"))))),
		(pz1 = sym(snoiseVec3(add(p, $(D, "yyx"))))),
		ret(
			div(
				vec3(
					add(sub(sub($z(py1), $z(py0)), $y(pz1)), $y(pz0)),
					add(sub(sub($x(pz1), $x(pz0)), $z(px1)), $z(px0)),
					add(sub(sub($y(px1), $y(px0)), $x(py1)), $x(py0))
				),
				mul(2, e)
			)
		),
	];
});