如何解决div里面不能放three.js动画
当我将使用three.js 完成的动画放在body 上时，效果非常好。
当我尝试将动画放入 div 时出现问题。我整天都在尝试，但无法正常工作。与将动画放在 body 上的那个版本相比，我在 js 文件中唯一更改的是这一行：从 document.body.appendChild(container); 到 document.getElementById('for_three').appendChild(container);。如果我在 js 文件中将 document.getElementById('for_three').appendChild(container); 改回 document.body.appendChild(container); 并切出这个 <div id="for_three"></div> 的 html 文件，那么动画会放在 body 上并且工作得很好。但我不希望它在 body 上，我希望它在 div 内。
我无法用代码片段（完整的three.js文件）发布这个问题，因为帖子太长了。但是代码和this one完全一样。
html 文件：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Three.js animation</title>
<style>
body { margin: 0; }
</style>
<link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
<script src="three.js"></script>
<div id="for_three"></div>
</body>
</html>
css 文件：
#for_three {
position: absolute;
width: 50%;
height: 50%;
margin-top: 10%;
margin-left: 25%;
background-color: bisque;
}
js文件：
// three.js - https://github.com/mrdoob/three.js
var SEPARATION = 100,AMOUNTX = 100,AMOUNTY = 70;
var container;
var camera,scene,renderer;
var particles,particle,count = 0;
var mouseX = 85,mouseY = -342;
var windowHalfX = window.innerWidth / 2;
var windowHalfY = window.innerHeight / 2;
init();
animate();
function init() {
container = document.createElement('div');
document.getElementById('for_three').appendChild(container);
camera = new THREE.PerspectiveCamera(120,window.innerWidth / window.innerHeight,1,10000);
camera.position.z = 1000;
scene = new THREE.Scene();
particles = new Array();
var PI2 = Math.PI * 2;
var material = new THREE.ParticleCanvasMaterial({
color: 0x000000,program: function(context) {
context.beginPath();
context.arc(0,.6,PI2,true);
context.fill();
}
});
var i = 0;
for (var ix = 0; ix < AMOUNTX; ix++) {
for (var iy = 0; iy < AMOUNTY; iy++) {
particle = particles[i++] = new THREE.Particle(material);
particle.position.x = ix * SEPARATION - ((AMOUNTX * SEPARATION) / 2);
particle.position.z = iy * SEPARATION - ((AMOUNTY * SEPARATION) / 2);
scene.add(particle);
}
}
renderer = new THREE.CanvasRenderer();
renderer.setSize(window.innerWidth,window.innerHeight);
container.appendChild(renderer.domElement);
document.addEventListener('mousemove',onDocumentMouseMove,false);
document.addEventListener('touchstart',onDocumentTouchStart,false);
document.addEventListener('touchmove',onDocumentTouchMove,false);
window.addEventListener('resize',onWindowResize,false);
}
function onWindowResize() {
windowHalfX = window.innerWidth / 2;
windowHalfY = window.innerHeight / 2;
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize(window.innerWidth,window.innerHeight);
}
function onDocumentMouseMove(event) {
mouseX = event.clientX - windowHalfX;
mouseY = event.clientY - windowHalfY;
}
function onDocumentTouchStart(event) {
if (event.touches.length === 1) {
event.preventDefault();
mouseX = event.touches[0].pageX - windowHalfX;
mouseY = event.touches[0].pageY - windowHalfY;
}
}
function onDocumentTouchMove(event) {
if (event.touches.length === 1) {
event.preventDefault();
mouseX = event.touches[0].pageX - windowHalfX;
mouseY = event.touches[0].pageY - windowHalfY;
}
}
function animate() {
requestAnimationFrame(animate);
render();
}
function render() {
camera.position.x += (mouseX - camera.position.x) * .05;
camera.position.y += (-mouseY - camera.position.y) * .05;
camera.lookAt(scene.position);
var i = 0;
for (var ix = 0; ix < AMOUNTX; ix++) {
for (var iy = 0; iy < AMOUNTY; iy++) {
particle = particles[i++];
particle.position.y = (Math.sin((ix + count) * 0.3) * 50) + (Math.sin((iy + count) * 0.5) * 50);
particle.scale.x = particle.scale.y = (Math.sin((ix + count) * 0.3) + 1) * 2 + (Math.sin((iy + count) * 0.5) + 1) * 2;
}
}
renderer.render(scene,camera);
count += 0.1;
}
提前致谢。
解决方法
问题在于您正在之前在文档中创建 <div id="for_three"></div> 之前执行脚本。因此，当您的脚本尝试查找 div 时，它还不存在。这是因为浏览器从上到下读取您的 HTML。只需更改顺序，使您的 <script> 标记位于文档末尾：
<body>
<div id="for_three"></div>
<script src="three.js"></script>
</body>
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