Function buildPermutationTable

simplex-noise.ts:484–500

(random: RandomFn)

 * @private
 */
export function buildPermutationTable(random: RandomFn): Uint8Array {
  const tableSize = 512;
  const p = new Uint8Array(tableSize);
  for (let i = 0; i < tableSize / 2; i++) {
    p[i] = i;
  }
  for (let i = 0; i < tableSize / 2 - 1; i++) {
    const r = i + ~~(random() * (256 - i));
    const aux = p[i];
    p[i] = p[r];
    p[r] = aux;
  }
  for (let i = 256; i < tableSize; i++) {
    p[i] = p[i - 256];
  }
  return p;
}