function init() {
  class Point {
    constructor(x, y) {
      this.x = x;
      this.y = y;
    }

    add(that) {
      return new Point(
        this.x + that.x,
        this.y + that.y
      );
    }

    sub(that) {
      return new Point(
        this.x - that.x,
        this.y - that.y
      );
    }

    dist(that) {
      let a = this.x - that.x;
      let b = this.y - that.y;
      return Math.sqrt(a * a + b * b)
    }
  }

  class Face {
    indices = [];

    constructor(a, b, c, d) {
      this.indices.push(a);
      this.indices.push(b);
      this.indices.push(c);
      this.indices.push(d);
    }
  }

  class Cloth {
    VertexWeight = 1;

    geometry = new THREE.Geometry();

    faces = [];

    vertexWeights = [];

    springs = [];

    getSprings(faceIndex) {

    }

    static CreateBasic(width, height, numPointsWidth, numPointsHeight) {
      let vertices = [];
      let faces = [];

      let stepWidth = width / (numPointsWidth - 1);
      let stepHeight = height / (numPointsHeight - 1);

      for (let y = 0; y < numPointsHeight; y++) {
        for (let x = 0; x < numPointsWidth; x++) {
          vertices.push(
            new THREE.Vector3(x * stepWidth, height - y * stepHeight, 0)
          );
        }
      }

      function getVertexIndex(x, y) {
        return y * numPointsWidth + x;
      }
      
      for (let y = 0; y < numPointsHeight - 1; y++) {
        for (let x = 0; x < numPointsWidth - 1; x++) {
          faces.push(
            new Face(
              getVertexIndex(x, y),
              getVertexIndex(x, y + 1),
              getVertexIndex(x + 1, y),
              getVertexIndex(x + 1, y + 1),
            )
          );
        }
      }

      return this.CreateExplicit(vertices, faces);
    }

    static CreateExplicit(vertices, faces) {
      let result = new Cloth();

      for (let i in vertices) {
        result.geometry.vertices.push(vertices[i]);
        result.vertexWeights.push(0);
      }
      for (let i in faces) {
        let face = faces[i];

        result.geometry.faces.push(new THREE.Face3(
          face.a, face.b, face.c
        ));
        result.geometry.faces.push(new THREE.Face3(
          face.c, face.b, face.d
        ));
        
        let xLength =
          result.geometry.vertices[face.b]
          .sub(result.geometry.vertices[face.a])
          .length();
        let yLength =
          result.geometry.vertices[face.c]
          .sub(result.geometry.vertices[face.a])
          .length();
        let weight = xLength * yLength / 2;

        xLength =
          result.geometry.vertices[face.b]
          .sub(result.geometry.vertices[face.d])
          .length();
        yLength =
          result.geometry.vertices[face.c]
          .sub(result.geometry.vertices[face.d])
          .length();

        weight += xLength * yLength / 2;

        result.vertexWeights[face.a] += weight / 4;
        result.vertexWeights[face.b] += weight / 4;
        result.vertexWeights[face.c] += weight / 4;
        result.vertexWeights[face.d] += weight / 4;
      }

      result.geometry.computeBoundingSphere();

      return result;
    }
  }

  let mousePos = new Point();

  const canvasSpace = 200;

  const scene = new THREE.Scene();
  const camera = new THREE.PerspectiveCamera(75, window.innerWidth / (window.innerHeight - canvasSpace), 0.1, 1000);

  const renderer = new THREE.WebGLRenderer();
  renderer.setSize(window.innerWidth, window.innerHeight - canvasSpace);
  document.getElementById("threejscontainer").appendChild(renderer.domElement);

  const directionalLight = new THREE.DirectionalLight(0xffffff, 1);
  scene.add(directionalLight);

  let cloth = Cloth.CreateBasic(10, 10, 4, 4);
  const material = new THREE.MeshBasicMaterial({ color: 0x00ff00 });
  const mesh = new THREE.Mesh(cloth.geometry, material);
  scene.add(mesh);

  camera.position.y = 5;
  camera.position.z = 10;

  function animate(dt) {
    requestAnimationFrame(animate);
    renderer.render(scene, camera);
  }

  let canvas = document.getElementsByTagName("canvas")[0];
  let resize = function () {
    w = window.innerWidth;
    h = window.innerHeight - 200;
    canvas.width = w;
    canvas.height = h;
  }
  window.onresize = resize;
  resize();
  if (canvas.getContext) {
    ctx = canvas.getContext('2d');
    animate(performance.now());
  }
  canvas.onmousemove = (evt) => {
    mousePos.x = evt.clientX;
    mousePos.y = evt.clientY;
  };
}