let waterLevel = 0.3;

​

let sun;

​

let heightMap, finalScreen;

​

let shadowShader;

​

​

function preload() {

  shadowShader = loadShader("/shaders/shader.vert", "/shaders/shader.frag");

}

​

​

function setup() {

  createCanvas(800, 800);

  describe("A mountainous sand, grass, and stone island in a light blue ocean. The mountains cast shadows on the terrain and ocean surface.")

  heightMap = createGraphics(width, height);

  finalScreen = createGraphics(width, height, WEBGL);

  sun = createVector(0, 0, 1); // sun at 1 unit high

  noiseSeed(random());

  generate();

  finalScreen.shader(shadowShader);

}

​

function draw() {

  sun.x = mouseX/width;

  sun.y = mouseY/height;

// Uncomment these lines for animated shadows  

//   const timeSlow = 10000;

//   sun.x = cos(millis()/timeSlow) * 0.75 + 0.5;

//   sun.y = sin(millis()/timeSlow) * 0.75 + 0.5;

//   sun.z = 1; //cos(millis()/timeSlow * 5) * 0.6 + 1;

  shadowShader.setUniform("height", heightMap);

  shadowShader.setUniform("sunPos", [sun.x, sun.y, sun.z]);

  shadowShader.setUniform("pix", [1/width, 1/height, 0]);

  shadowShader.setUniform("waterLevel", waterLevel);

  shadowShader.setUniform("millis", millis());

  finalScreen.clear();

  finalScreen.rect(0, 0, width, height);

  image(finalScreen, 0, 0, width, height);

}

​

​

// Island generation stuff

// not that exciting, just use perlin noise to make

// some basic island terrain

​

function generate() {

  // Loop through each pixel and fill the height and colour maps

  for(let i = 0; i < width; i ++) {

    for(let j = 0; j < height; j ++) {

      tile(i, j);

    }

  }

}

​

function tile(x, y) {

  // Get the nois value

  let n = noiseVal(x, y);

  // Draw it in grey scale onto the height map

  heightMap.noStroke();

  heightMap.fill(255 * n);

  heightMap.square(x, y, 1);

}

​

function noiseVal(x, y) {

  // Use perlin noise for basic terrain

  let n = noise(x * noiseScale, y * noiseScale);

  // Shape terrain to be islands in the middle

  n *= islandMod(x, y);

  return n;

}

​

// Squashes terrain further from the centre so that

// outsides are guarenteed to be water

function islandMod(x, y) {

  let maxD = min(width, height);

  maxD = (maxD/2) * (maxD/2);

  const dx = width/2 - x;

  const dy = height/2 - y;

  const dSq = (dx * dx) + (dy * dy);

  return map(dSq, 0, maxD, 1, 0);

}