let Pi = vec4.add(vec4.floor(v2.xyxy), new vec4(0.0, 0.0, 1.0, 1.0));

  Pi = vec4.mod289(Pi); // To avoid truncation effects in permutation

​

  const Pf = vec4.sub(vec4.fract(v2.xyxy), new vec4(0.0, 0.0, 1.0, 1.0));

​

  const ix = Pi.xzxz;

  const iy = Pi.yyww;

  const fx = Pf.xzxz;

  const fy = Pf.yyww;

​

  const i = vec4.permute(vec4.add(vec4.permute(ix), iy));

  let gx = vec4.fract(vec4.mulByNum(i, 1.0 / 41.0));

  gx = vec4.mulByNum(gx, 2.0);

  gx = vec4.subNum(gx, 1.0);

  const gy = vec4.subNum(vec4.abs(gx), 0.5);

  const tx = vec4.addNum(vec4.floor(gx), 0.5);

​

  gx = vec4.sub(gx, tx);

​

  let g00 = new vec2(gx.x, gy.x);

  let g10 = new vec2(gx.y, gy.y);

  let g01 = new vec2(gx.z, gy.z);

  let g11 = new vec2(gx.w, gy.w);

​

  const norm = vec4.taylorInvSqrt(

    new vec4(

      vec2.dot(g00, g00),

      vec2.dot(g01, g01),

      vec2.dot(g10, g10),

      vec2.dot(g11, g11)

    )

  );

​

  g00 = vec2.mulByNum(g00, norm.x);

  g01 = vec2.mulByNum(g01, norm.y);

  g10 = vec2.mulByNum(g10, norm.z);

  g11 = vec2.mulByNum(g11, norm.w);

​

  const n00 = vec2.dot(g00, new vec2(fx.x, fy.x));

  const n10 = vec2.dot(g10, new vec2(fx.y, fy.y));

  const n01 = vec2.dot(g01, new vec2(fx.z, fy.z));

  const n11 = vec2.dot(g11, new vec2(fx.w, fy.w));

​

  const fade_xy = vec2.fade(Pf.xy);

  const n_x = vec2.mix(new vec2(n00, n01), new vec2(n10, n11), fade_xy.x);

  const n_xy = math.mix(n_x.x, n_x.y, fade_xy.y);

​

  return 2.3 * n_xy;

}

​