plasma_height_map1.js

// size of our height maps
const mapSize = 1024;

// returns the distance of point x,y from the origin 0,0
const distance = (x, y) => Math.sqrt(x * x + y * y);

// init height map 1
const heightMap1 = [];
for (let u = 0; u < mapSize; u++) {
  for (let v = 0; v < mapSize; v++) {
    // index of coordinate in height map array
    const i = u * mapSize + v;

    // u,v are coordinates with origin at upper left corner
    // cx and cy are coordinates with origin at the
    // center of the map
    const cx = u - mapSize / 2;
    const cy = v - mapSize / 2;

    // distance from middle of map
    const d = distance(cx, cy);

    // stretching so we get the desired ripple density on our map
    const stretch = (3 * Math.PI) / (mapSize / 2);

    // wavy height value between -1 and 1
    const ripple = Math.sin(d * stretch);

    // wavy height value normalized to 0..1
    const normalized = (ripple + 1) / 2;

    // height map value 0..128, integer
    heightMap1[i] = Math.floor(normalized * 128);
  }
}