### fractal terrain

fractal terrain

```// You can find the Turtle API reference here: https://turtletoy.net/syntax
Canvas.setpenopacity(1);

// Global code will be evaluated once.
const turtle = new Turtle();
turtle.penup();
/////////////////////////////////////
const size = 512; // try 256 or 128
const water = 4; // 0 for no water
let randomLevel = 60;
let seed = (Math.random() * 100000) | 0;
/////////////////////////////////////
console.log("seed: " + seed);
function random () {
seed = (seed * 16807) % 2147483647;
return (seed - 1) / 2147483646;
}
const hmap = [];
for (let i = 0; i <= size; i++) hmap[i] = new Float32Array(size + 1);
const nbits = size.toString(2).length - 1;
const rnd = () => randomLevel * (-1 + 2 * random());
let t = 1;
let x = size / 2;
for (let s = 1; s <= nbits; s++) {
for (let v = 0; v <= size; v += 2 * x) {
for (let n = 1; n <= t; n += 2) {
hmap[n * x][v] = ((hmap[(n - 1) * x][v] + hmap[(n + 1) * x][v]) / 2) + rnd();
hmap[v][n * x] = ((hmap[v][(n - 1) * x] + hmap[v][(n + 1) * x]) / 2) + rnd();
}
}
for (let n = 1; n <= t; n += 2) {
for (let m = 1; m <= t; m += 2) {
hmap[n * x][m * x] = (0.25 * (
hmap[n * x + x][m * x] +
hmap[n * x - x][m * x] +
hmap[n * x][m * x + x] +
hmap[n * x][m * x - x])
) + rnd();
}
}
t = 2 * t + 1;
x /= 2;
randomLevel /= 2;
}
for (let w = 0; w <= size; w++) {
for (let z = 0; z <= size; z++) {
if (hmap[w][z] < 0) hmap[w][z] = 0;
}
}
const line = new Float32Array(size + 1);
const r = 200 / size;
let pen = false;
for (let w = 0; w <= size; w++) {
let k = 0;
pen = false;
for (let z = 0; z <= size; z++) {
let xe = r * z;
let ye = r * 0.66 * w + hmap[z][w] * 1;
if (ye <= line[z] || (hmap[z][w] === 0 && w / water !== ((w / water)|0))) {
if (pen === true) {
turtle.up();
pen = false;
}
} else {
if (pen === false) {
pen = true;
}
turtle.goto(-100 + xe, 100 - ye);
turtle.down();
line[z] = ye;
}
}
turtle.up();
}```