@thi.ng/shader-ast-stdlib/noise/simplex2.js

Function collection for modular GPGPU / shader programming with @thi.ng/shader-ast

import { F, V2 } from "@thi.ng/shader-ast/api/types";
import { assign } from "@thi.ng/shader-ast/ast/assign";
import { ternary } from "@thi.ng/shader-ast/ast/controlflow";
import { defn, ret } from "@thi.ng/shader-ast/ast/function";
import {
  FLOAT05,
  FLOAT1,
  VEC3_0,
  float,
  vec2,
  vec3,
  vec4
} from "@thi.ng/shader-ast/ast/lit";
import { add, gt, mul, mulSelf, sub } from "@thi.ng/shader-ast/ast/ops";
import { $, $x, $xy, $y } from "@thi.ng/shader-ast/ast/swizzle";
import { sym } from "@thi.ng/shader-ast/ast/sym";
import {
  abs,
  dot,
  floor,
  fract,
  max,
  mod
} from "@thi.ng/shader-ast/builtin/math";
import { magSq2 } from "../math/magsq.js";
import { permute3 } from "./permute.js";
const snoise2 = defn(F, "snoise2", [V2], (v) => {
  let C;
  let i;
  let i1;
  let x0;
  let x12;
  let p;
  let m;
  let x;
  let h;
  let ox;
  let a0;
  let g;
  return [
    C = sym(
      vec4(
        0.211324865405187,
        0.366025403784439,
        -0.577350269189626,
        0.024390243902439
      )
    ),
    i = sym(floor(add(v, dot(v, $(C, "yy"))))),
    x0 = sym(add(sub(v, i), dot(i, $(C, "xx")))),
    i1 = sym(ternary(gt($x(x0), $y(x0)), vec2(1, 0), vec2(0, 1))),
    x12 = sym(sub(add($(x0, "xyxy"), $(C, "xxzz")), vec4(i1, 0, 0))),
    assign(i, mod(i, float(289))),
    p = sym(
      permute3(
        add(
          permute3(add(vec3(0, $y(i1), 1), $y(i))),
          add(vec3(0, $x(i1), 1), $x(i))
        )
      )
    ),
    m = sym(
      max(
        sub(
          FLOAT05,
          vec3(magSq2(x0), magSq2($xy(x12)), magSq2($(x12, "zw")))
        ),
        VEC3_0
      )
    ),
    mulSelf(m, m),
    mulSelf(m, m),
    x = sym(sub(mul(2, fract(mul(p, $(C, "www")))), FLOAT1)),
    h = sym(sub(abs(x), FLOAT05)),
    ox = sym(floor(add(x, FLOAT05))),
    a0 = sym(sub(x, ox)),
    mulSelf(
      m,
      sub(
        1.79284291400159,
        mul(0.85373472095314, add(mul(a0, a0), mul(h, h)))
      )
    ),
    g = sym(vec3(add(mul($x(a0), $x(x0)), mul($x(h), $y(x0))))),
    assign(
      $(g, "yz"),
      add(mul($(a0, "yz"), $(x12, "xz")), mul($(h, "yz"), $(x12, "yw")))
    ),
    ret(mul(130, dot(m, g)))
  ];
});
export {
  snoise2
};