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414 lines
17 KiB
414 lines
17 KiB
<!DOCTYPE html><html lang="zh"><head>
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<meta charset="utf-8">
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<title>清除</title>
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<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
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<meta name="twitter:card" content="summary_large_image">
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<meta name="twitter:site" content="@threejs">
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<meta name="twitter:title" content="Three.js – Cleanup">
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<meta property="og:image" content="https://threejs.org/files/share.png">
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<link rel="shortcut icon" href="/files/favicon_white.ico" media="(prefers-color-scheme: dark)">
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<link rel="shortcut icon" href="/files/favicon.ico" media="(prefers-color-scheme: light)">
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<link rel="stylesheet" href="/manual/resources/lesson.css">
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<link rel="stylesheet" href="/manual/resources/lang.css">
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<!-- Import maps polyfill -->
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<!-- Remove this when import maps will be widely supported -->
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<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>
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<script type="importmap">
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{
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"imports": {
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"three": "../../build/three.module.js"
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}
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}
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</script>
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</head>
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<body>
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<div class="container">
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<div class="lesson-title">
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<h1>清除</h1>
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</div>
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<div class="lesson">
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<div class="lesson-main">
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<p>Three.js应用经常使用大量的内存。一个3D模型的所有节点，可能占用1-20M内存。
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一个模型可能会使用很多纹理，即使它们被压缩成了图片文件，也必须被展开成为未压缩的形态来使用。每个 1024 x 1024 大小的纹理会占用4-5M内存。</p>
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<p>大多数的three.js应用在初始化的时候加载资源，并且一直使用这些资源直到页面关闭。但是，如果你想随时间的变动加载和改变资源怎么办呢？</p>
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<p>不像大多数的JavaScript库，three.js不能自动的清除这些资源。
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如果你切换页面，浏览器会清除这些资源，其它时候如何管理它们取决于你。这是WebGL设计的问题，three.js没有追索权只能将释放资源的责任托付给你。</p>
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<p>通过在<a href="textures.html">纹理</a>、
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<a href="primitives.html">图元</a>和
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<a href="materials.html">材质</a>对象上调用<code class="notranslate" translate="no">dispose</code>方法来释放资源
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</p>
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<p>你可以手动来处理。起初，你可能创建了一些资源。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const boxGeometry = new THREE.BoxGeometry(...);
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const boxTexture = textureLoader.load(...);
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const boxMaterial = new THREE.MeshPhongMaterial({map: texture});
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</pre>
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<p>然后，当你处理完了它们，可以释放它们</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">boxGeometry.dispose();
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boxTexture.dispose();
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boxMaterial.dispose();
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</pre>
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<p>随着你使用越来越多的资源，这将会变得越来越乏味。</p>
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<p>为了减少一些乏味的工作，让我们创建一个类来跟踪这些资源。我们会请求这个类来帮我们做清除的工作。
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</p>
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<p>这个类一开始是这个样子。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">class ResourceTracker {
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constructor() {
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this.resources = new Set();
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}
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track(resource) {
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if (resource.dispose) {
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this.resources.add(resource);
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}
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return resource;
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}
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untrack(resource) {
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this.resources.delete(resource);
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}
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dispose() {
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for (const resource of this.resources) {
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resource.dispose();
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}
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this.resources.clear();
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}
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}
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</pre>
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<p>让我们在<a href="textures.html">纹理文章</a>中的例子中使用这个类。我们可以创建一个这个类的实例。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const resTracker = new ResourceTracker();
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</pre>
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<p>然后为了让这个类的使用更加地简单，让我们来为<code class="notranslate" translate="no">track</code>方法创建一个绑定函数。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const resTracker = new ResourceTracker();
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+const track = resTracker.track.bind(resTracker);
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</pre>
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<p>现在，我们只需要在我们创建的每个图元、纹理、材质对象上调用<code class="notranslate" translate="no">track</code>方法就可以使用它。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const boxWidth = 1;
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const boxHeight = 1;
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const boxDepth = 1;
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-const geometry = new THREE.BoxGeometry(boxWidth, boxHeight, boxDepth);
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+const geometry = track(new THREE.BoxGeometry(boxWidth, boxHeight, boxDepth));
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const cubes = []; // an array we can use to rotate the cubes
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const loader = new THREE.TextureLoader();
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-const material = new THREE.MeshBasicMaterial({
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- map: loader.load('resources/images/wall.jpg'),
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-});
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+const material = track(new THREE.MeshBasicMaterial({
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+ map: track(loader.load('resources/images/wall.jpg')),
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+}));
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const cube = new THREE.Mesh(geometry, material);
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scene.add(cube);
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cubes.push(cube); // add to our list of cubes to rotate
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</pre>
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<p>然后，我们从场景中移除这些立方体，再然后调用<code class="notranslate" translate="no">resTracker.dispose</code>来释放它们。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">for (const cube of cubes) {
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scene.remove(cube);
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}
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cubes.length = 0; // clears the cubes array
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resTracker.dispose();
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</pre>
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<p>这起作用了，但是我发现必须从场景中移除立方体有些乏味。让我们给<code class="notranslate" translate="no">ResourceTracker</code>增加这个功能。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">class ResourceTracker {
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constructor() {
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this.resources = new Set();
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}
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track(resource) {
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- if (resource.dispose) {
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+ if (resource.dispose || resource instanceof THREE.Object3D) {
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this.resources.add(resource);
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}
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return resource;
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}
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untrack(resource) {
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this.resources.delete(resource);
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}
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dispose() {
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for (const resource of this.resources) {
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- resource.dispose();
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+ if (resource instanceof THREE.Object3D) {
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+ if (resource.parent) {
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+ resource.parent.remove(resource);
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+ }
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+ }
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+ if (resource.dispose) {
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+ resource.dispose();
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+ }
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+ }
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this.resources.clear();
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}
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}
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</pre>
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<p>现在我们可以跟踪这些立方体了</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const material = track(new THREE.MeshBasicMaterial({
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map: track(loader.load('resources/images/wall.jpg')),
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}));
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const cube = track(new THREE.Mesh(geometry, material));
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scene.add(cube);
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cubes.push(cube); // add to our list of cubes to rotate
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</pre>
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<p>我们不再需要编码从场景中移除这些立方体了。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">-for (const cube of cubes) {
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- scene.remove(cube);
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-}
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cubes.length = 0; // clears the cube array
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resTracker.dispose();
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</pre>
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<p>让我们来调整一下代码，这样我们可以重新添加立方体、纹理和材质。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const scene = new THREE.Scene();
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*const cubes = []; // just an array we can use to rotate the cubes
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+function addStuffToScene() {
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const resTracker = new ResourceTracker();
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const track = resTracker.track.bind(resTracker);
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const boxWidth = 1;
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const boxHeight = 1;
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const boxDepth = 1;
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const geometry = track(new THREE.BoxGeometry(boxWidth, boxHeight, boxDepth));
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const loader = new THREE.TextureLoader();
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const material = track(new THREE.MeshBasicMaterial({
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map: track(loader.load('resources/images/wall.jpg')),
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}));
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const cube = track(new THREE.Mesh(geometry, material));
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scene.add(cube);
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cubes.push(cube); // add to our list of cubes to rotate
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+ return resTracker;
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+}
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</pre>
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<p>让我们来编写一些随着时间变动添加和移除物体的代码。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">function waitSeconds(seconds = 0) {
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return new Promise(resolve => setTimeout(resolve, seconds * 1000));
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}
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async function process() {
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for (;;) {
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const resTracker = addStuffToScene();
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await wait(2);
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cubes.length = 0; // remove the cubes
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resTracker.dispose();
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await wait(1);
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}
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}
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process();
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</pre>
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<p>代码将会创建立方体、纹理和材质，等待2秒，然后释放它们，然后等待1秒，重复这个过程。</p>
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<p></p><div translate="no" class="threejs_example_container notranslate">
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<div><iframe class="threejs_example notranslate" translate="no" style=" " src="/manual/examples/resources/editor.html?url=/manual/examples/cleanup-simple.html"></iframe></div>
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<a class="threejs_center" href="/manual/examples/cleanup-simple.html" target="_blank">点击此处打开独立窗口</a>
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</div>
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<p></p>
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<p>这好像能工作了。</p>
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<p>对于加载文件来说，还需要一点额外的工作。大多数的加载器仅仅返回一个<a href="/docs/#api/en/core/Object3D"><code class="notranslate" translate="no">Object3D</code></a>
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对象，作为它加载的层次对象的根节点，因此我们需要去发现所有的这些资源是哪些。</p>
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<p>让我们更新<code class="notranslate" translate="no">ResourceTracker</code>来试着去实现它。</p>
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<p>首先，我们来检测这个物体是否是一个<a href="/docs/#api/en/core/Object3D"><code class="notranslate" translate="no">Object3D</code></a>，然后跟踪它的图元、材质和子对象。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">class ResourceTracker {
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constructor() {
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this.resources = new Set();
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}
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track(resource) {
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if (resource.dispose || resource instanceof THREE.Object3D) {
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this.resources.add(resource);
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}
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+ if (resource instanceof THREE.Object3D) {
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+ this.track(resource.geometry);
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+ this.track(resource.material);
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+ this.track(resource.children);
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+ }
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return resource;
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}
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...
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}
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</pre>
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<p>现在，因为任意的<code class="notranslate" translate="no">resource.geometry</code>、<code class="notranslate" translate="no">resource.material</code>和<code class="notranslate" translate="no">resource.children</code>有可能为null或undefined，
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我们将在<code class="notranslate" translate="no">track</code>的入口执行检查。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">class ResourceTracker {
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constructor() {
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this.resources = new Set();
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}
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track(resource) {
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+ if (!resource) {
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+ return resource;
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+ }
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if (resource.dispose || resource instanceof THREE.Object3D) {
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this.resources.add(resource);
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}
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if (resource instanceof THREE.Object3D) {
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this.track(resource.geometry);
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this.track(resource.material);
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this.track(resource.children);
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}
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return resource;
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}
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...
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}
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</pre>
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<p>同时，因为<code class="notranslate" translate="no">resource.children</code>是一个数组，
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同时<code class="notranslate" translate="no">resource.material</code>也可能是数组，让我们对数组做检测。
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</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">class ResourceTracker {
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constructor() {
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this.resources = new Set();
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}
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track(resource) {
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if (!resource) {
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return resource;
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}
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+ // handle children and when material is an array of materials.
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+ if (Array.isArray(resource)) {
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+ resource.forEach(resource => this.track(resource));
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+ return resource;
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+ }
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if (resource.dispose || resource instanceof THREE.Object3D) {
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this.resources.add(resource);
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}
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if (resource instanceof THREE.Object3D) {
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this.track(resource.geometry);
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this.track(resource.material);
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this.track(resource.children);
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}
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return resource;
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}
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...
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}
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</pre>
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<p>最后我们需要遍历这些材质的属性和uniforms来寻找纹理。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">class ResourceTracker {
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constructor() {
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this.resources = new Set();
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}
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track(resource) {
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if (!resource) {
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return resource;
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}
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* // handle children and when material is an array of materials or
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* // uniform is array of textures
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if (Array.isArray(resource)) {
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resource.forEach(resource => this.track(resource));
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return resource;
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}
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if (resource.dispose || resource instanceof THREE.Object3D) {
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this.resources.add(resource);
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}
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if (resource instanceof THREE.Object3D) {
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this.track(resource.geometry);
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this.track(resource.material);
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this.track(resource.children);
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- }
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+ } else if (resource instanceof THREE.Material) {
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+ // We have to check if there are any textures on the material
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+ for (const value of Object.values(resource)) {
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+ if (value instanceof THREE.Texture) {
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+ this.track(value);
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+ }
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+ }
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+ // We also have to check if any uniforms reference textures or arrays of textures
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+ if (resource.uniforms) {
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+ for (const value of Object.values(resource.uniforms)) {
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+ if (value) {
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+ const uniformValue = value.value;
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+ if (uniformValue instanceof THREE.Texture ||
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+ Array.isArray(uniformValue)) {
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+ this.track(uniformValue);
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+ }
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+ }
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+ }
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+ }
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+ }
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return resource;
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}
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...
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}
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</pre>
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<p>让我们来使用<a href="load-gltf.html">“加载gltf文件文章“</a>中的例子，让它能够加载和释放文件。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const gltfLoader = new GLTFLoader();
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function loadGLTF(url) {
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return new Promise((resolve, reject) => {
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gltfLoader.load(url, resolve, undefined, reject);
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});
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}
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function waitSeconds(seconds = 0) {
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return new Promise(resolve => setTimeout(resolve, seconds * 1000));
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}
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const fileURLs = [
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'resources/models/cartoon_lowpoly_small_city_free_pack/scene.gltf',
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'resources/models/3dbustchallange_submission/scene.gltf',
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'resources/models/mountain_landscape/scene.gltf',
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'resources/models/simple_house_scene/scene.gltf',
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];
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async function loadFiles() {
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for (;;) {
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for (const url of fileURLs) {
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const resMgr = new ResourceTracker();
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const track = resMgr.track.bind(resMgr);
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const gltf = await loadGLTF(url);
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const root = track(gltf.scene);
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scene.add(root);
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// compute the box that contains all the stuff
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// from root and below
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const box = new THREE.Box3().setFromObject(root);
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const boxSize = box.getSize(new THREE.Vector3()).length();
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const boxCenter = box.getCenter(new THREE.Vector3());
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// set the camera to frame the box
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frameArea(boxSize * 1.1, boxSize, boxCenter, camera);
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await waitSeconds(2);
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renderer.render(scene, camera);
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resMgr.dispose();
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await waitSeconds(1);
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}
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}
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}
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loadFiles();
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</pre>
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<p>然后我们得到了</p>
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<p></p><div translate="no" class="threejs_example_container notranslate">
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<div><iframe class="threejs_example notranslate" translate="no" style=" " src="/manual/examples/resources/editor.html?url=/manual/examples/cleanup-loaded-files.html"></iframe></div>
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<a class="threejs_center" href="/manual/examples/cleanup-loaded-files.html" target="_blank">点击此处在独立窗口中打开</a>
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</div>
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<p></p>
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<p>关于代码的一些注释。</p>
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<p>如果我们想要加载2个或者更多的文件，并且想要随时地释放它们，我们将要每个文件使用一个<code class="notranslate" translate="no">ResourceTracker</code>。</p>
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<p>在上面中，我们只是在场景加载之后跟踪了<code class="notranslate" translate="no">gltf.scene</code>。
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根据<code class="notranslate" translate="no">ResourceTracker</code>的当前实现版本，它会跟踪刚刚加载的所有资源。如果我们向场景中添加了更多的资源，我们需要决定是否要跟踪它们。
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</p>
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<p>举例来说，在我们加载了一个角色之后，我们把一个工具放入它的手中，这是通过把工具成为手的子对象来实现的。因此工具将不会被释放。我猜更多的时候，这不是我们想要的。</p>
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<p>这带来了一个问题。当我起初写上面的<code class="notranslate" translate="no">ResourceTracker</code>的时候，
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我是在<code class="notranslate" translate="no">dispose</code>方法中遍历所有对象而不是在
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<code class="notranslate" translate="no">track</code>方法中。稍后，我就想到了上面的成为手的子对象的工具的这个例子，
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在<code class="notranslate" translate="no">track</code>方法中确切地跟踪哪些对象需要被释放更加地灵活，按理来说也更加地准确，因为我们可以跟踪从文件中加载了什么，而不是稍后从资源图中释放状态。
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</p>
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<p>诚实地说，我对ResourceTracker并不是100%满意。在3D引擎中，做这样的事情并不是很常见。我们不应该去猜测什么资源被加载了，我们应该知道。
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如果three.js能做出改变，所有的文件加载器返回能够引用所有加载资源的标准对象，就太好了。至少在这个时候，three.js在场景加载的时候并没有提供给我们其它的信息。因此，这个方法是有效的。</p>
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<p>我希望这个例子能给你带来帮助或者至少成为在three.js中如何释放资源的一份好的参考</p>
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</div>
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</div>
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</div>
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<script src="/manual/resources/prettify.js"></script>
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<script src="/manual/resources/lesson.js"></script>
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</body></html>
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