manual/examples/render-on-demand.html

<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - Rendering on Demand</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    </style>
  </head>
  <body>
    <canvas id="c" tabindex="1"></canvas>
  </body>
<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js",
    "three/addons/": "../../examples/jsm/"
  }
}
</script>

<script type="module">
import * as THREE from 'three';
import { OrbitControls } from 'three/addons/controls/OrbitControls.js';

function main() {

	const canvas = document.querySelector( '#c' );
	const renderer = new THREE.WebGLRenderer( { antialias: true, canvas } );

	const fov = 75;
	const aspect = 2; // the canvas default
	const near = 0.1;
	const far = 5;
	const camera = new THREE.PerspectiveCamera( fov, aspect, near, far );
	camera.position.z = 2;

	const controls = new OrbitControls( camera, canvas );
	controls.target.set( 0, 0, 0 );
	controls.update();

	const scene = new THREE.Scene();

	{

		const color = 0xFFFFFF;
		const intensity = 3;
		const light = new THREE.DirectionalLight( color, intensity );
		light.position.set( - 1, 2, 4 );
		scene.add( light );

	}

	const boxWidth = 1;
	const boxHeight = 1;
	const boxDepth = 1;
	const geometry = new THREE.BoxGeometry( boxWidth, boxHeight, boxDepth );

	function makeInstance( geometry, color, x ) {

		const material = new THREE.MeshPhongMaterial( { color } );

		const cube = new THREE.Mesh( geometry, material );
		scene.add( cube );

		cube.position.x = x;

		return cube;

	}

	makeInstance( geometry, 0x44aa88, 0 );
	makeInstance( geometry, 0x8844aa, - 2 );
	makeInstance( geometry, 0xaa8844, 2 );

	function resizeRendererToDisplaySize( renderer ) {

		const canvas = renderer.domElement;
		const width = canvas.clientWidth;
		const height = canvas.clientHeight;
		const needResize = canvas.width !== width || canvas.height !== height;
		if ( needResize ) {

			renderer.setSize( width, height, false );

		}

		return needResize;

	}

	function render() {

		if ( resizeRendererToDisplaySize( renderer ) ) {

			const canvas = renderer.domElement;
			camera.aspect = canvas.clientWidth / canvas.clientHeight;
			camera.updateProjectionMatrix();

		}

		renderer.render( scene, camera );

	}

	render();

	controls.addEventListener( 'change', render );
	window.addEventListener( 'resize', render );

	// note: this is a workaround for an OrbitControls issue
	// in an iframe. Will remove once the issue is fixed in
	// three.js
	window.addEventListener( 'mousedown', ( e ) => {

		e.preventDefault();
		window.focus();

	} );
	window.addEventListener( 'keydown', ( e ) => {

		e.preventDefault();

	} );

}

main();
</script>
</html>