Pen Settings



CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URLs added here will be added as <link>s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.

+ add another resource


Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource


Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.


Auto Save

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.


                <canvas id="c"></canvas>


                html, body {
  height: 100%;

#c {
  width: 100%;
  height: 100%;
  display: block;


Automatically set the camera vertical FOV so that there's always a square area visible in the centre of the viewport, regardless of size and dimensions (the red square is just to show it works)

Math.degrees = function(radians) {
  return radians * 180 / Math.PI;

(function() {
  'use strict';

  //setup canvas, renderer
  const canvas = document.querySelector('#c');
  const renderer = new THREE.WebGLRenderer({canvas});

  //setup camera - camera defaults to looking down -Z axis with +Y up
  const fov = 90;         //not much point in setting this as gets overridden by setFOV
  const aspect = 1;       //not much point in setting this as gets overridden by setFOV
  const near = 0.1;
  const far = 5;
  const cameraDistance = 4;       //has to be less than far
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
  const worldSize = 10;         //this is the size in units of the square area that gets kept central
  camera.position.z = cameraDistance;

  //setup scene
  const scene = new THREE.Scene();

  //setup plane mesh
  const plane_dim = worldSize;        //to visualise the worldsize
  const plane_geom = new THREE.PlaneGeometry(plane_dim, plane_dim);

  const plane_mat = new THREE.MeshPhongMaterial({
    color: 0xFF0000

  const plane_mesh = new THREE.Mesh(plane_geom, plane_mat);


  //setup one light
  const light_color = 0xFFFFFF;
  const light_intensity = 1;
  const light = new THREE.DirectionalLight(light_color, light_intensity);
  light.position.set(-1, 2, 3);

  function resizeRendererToDisplaySize() {
    const canvas = renderer.domElement;
    const pixelRatio = window.devicePixelRatio;
    const width = canvas.clientWidth * pixelRatio | 0;       //CSS width of canvas
    const height = canvas.clientHeight * pixelRatio | 0;     //CSS height of canvas
    const needResize = canvas.width !== width || canvas.height !== height;      //drawingbuffer width/height of canvas

    if (needResize) {
      //changes the canvas size
      renderer.setSize(width, height, false);

    return needResize;

  function setFOV() {
    const canvas = renderer.domElement;
    camera.aspect = canvas.clientWidth / canvas.clientHeight;

    if (camera.aspect < 1) {
      const vFOV = 2 * Math.atan((worldSize / camera.aspect) / (2 * cameraDistance));
      camera.fov = Math.degrees(vFOV);
    } else {
      const vFOV = 2 * Math.atan(worldSize / ( 2 * cameraDistance));
      camera.fov = Math.degrees(vFOV);


  //the time var is automatically passed in (can be called anything BTW)
  function render(time) {
    time *=0.001;     //convert time to seconds

    if (resizeRendererToDisplaySize()) {

    renderer.render(scene, camera);