You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.

166 lines
7.9 KiB

2 years ago
<!DOCTYPE html><html lang="zh"><head>
<meta charset="utf-8">
<title>渲染目标</title>
<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:site" content="@threejs">
<meta name="twitter:title" content="Three.js – 渲染目标">
<meta property="og:image" content="https://threejs.org/files/share.png">
<link rel="shortcut icon" href="/files/favicon_white.ico" media="(prefers-color-scheme: dark)">
<link rel="shortcut icon" href="/files/favicon.ico" media="(prefers-color-scheme: light)">
<link rel="stylesheet" href="/manual/resources/lesson.css">
<link rel="stylesheet" href="/manual/resources/lang.css">
<!-- Import maps polyfill -->
<!-- Remove this when import maps will be widely supported -->
<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>
<script type="importmap">
{
"imports": {
"three": "../../build/three.module.js"
}
}
</script>
<link rel="stylesheet" href="/manual/zh/lang.css">
</head>
<body>
<div class="container">
<div class="lesson-title">
<h1>渲染目标</h1>
</div>
<div class="lesson">
<div class="lesson-main">
<p>在three.js中,渲染目标大体上指的是可以被渲染的纹理。当它被渲染之后,你可以像使用其他纹理一样使用它。</p>
<p>让我们举个简单的例子。我们将从<a href="responsive.html">the article on responsiveness</a>开始。</p>
<p>渲染到渲染目标基本上跟通常的渲染一样。首先我们创建一个 <a href="/docs/#api/zh/renderers/WebGLRenderTarget"><code class="notranslate" translate="no">WebGLRenderTarget</code></a></p>
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const rtWidth = 512;
const rtHeight = 512;
const renderTarget = new THREE.WebGLRenderTarget(rtWidth, rtHeight);
</pre>
<p>然后我们需要一个 <a href="/docs/#api/zh/cameras/Camera"><code class="notranslate" translate="no">Camera</code></a> 和一个 <a href="/docs/#api/zh/scenes/Scene"><code class="notranslate" translate="no">Scene</code></a></p>
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const rtFov = 75;
const rtAspect = rtWidth / rtHeight;
const rtNear = 0.1;
const rtFar = 5;
const rtCamera = new THREE.PerspectiveCamera(rtFov, rtAspect, rtNear, rtFar);
rtCamera.position.z = 2;
const rtScene = new THREE.Scene();
rtScene.background = new THREE.Color('red');
</pre>
<p>注意我们设置长宽比(aspect)是相对渲染目标而言的,不是画布(canvas)。
正确的长宽比取决于我们要渲染的对象。在本例,我们要将渲染目标的纹理用在方块的一个面,基于方块的面我们设置长宽比为1.0。</p>
<p>我们将需要的东西添加到场景中。在本例我们使用灯光和三个方块<a href="responsive.html">from the previous article</a></p>
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">{
const color = 0xFFFFFF;
const intensity = 1;
const light = new THREE.DirectionalLight(color, intensity);
light.position.set(-1, 2, 4);
* rtScene.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);
* rtScene.add(cube);
cube.position.x = x;
return cube;
}
*const rtCubes = [
makeInstance(geometry, 0x44aa88, 0),
makeInstance(geometry, 0x8844aa, -2),
makeInstance(geometry, 0xaa8844, 2),
];
</pre>
<p>在上个例子中的 <a href="/docs/#api/zh/scenes/Scene"><code class="notranslate" translate="no">Scene</code></a><a href="/docs/#api/zh/cameras/Camera"><code class="notranslate" translate="no">Camera</code></a> 保持不变,我们将在画布中继续使用它们,只需要添加渲染的物体。</p>
<p>让我们添加使用了渲染目标纹理的方块。</p>
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const material = new THREE.MeshPhongMaterial({
map: renderTarget.texture,
});
const cube = new THREE.Mesh(geometry, material);
scene.add(cube);
</pre>
<p>现在在渲染的时候,我们首先将渲染目标的场景(rtScene),渲染到渲染目标(注:这里有点绕,需要结合代码理解)。</p>
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">function render(time) {
time *= 0.001;
...
// rotate all the cubes in the render target scene
rtCubes.forEach((cube, ndx) =&gt; {
const speed = 1 + ndx * .1;
const rot = time * speed;
cube.rotation.x = rot;
cube.rotation.y = rot;
});
// draw render target scene to render target
renderer.setRenderTarget(renderTarget);
renderer.render(rtScene, rtCamera);
renderer.setRenderTarget(null);
</pre>
<p>然后我们在画布中,渲染使用了渲染目标纹理的方块的场景。</p>
<pre class="prettyprint showlinemods notranslate lang-js" translate="no"> // rotate the cube in the scene
cube.rotation.x = time;
cube.rotation.y = time * 1.1;
// render the scene to the canvas
renderer.render(scene, camera);
</pre>
<p>就是这样啦</p>
<p></p><div translate="no" class="threejs_example_container notranslate">
<div><iframe class="threejs_example notranslate" translate="no" style=" " src="/manual/examples/resources/editor.html?url=/manual/examples/render-target.html"></iframe></div>
<a class="threejs_center" href="/manual/examples/render-target.html" target="_blank">点击此处在新标签页中打开</a>
</div>
<p></p>
<p>方块是红色的,这是因为我们设置了 <code class="notranslate" translate="no">rtScene</code><code class="notranslate" translate="no">background</code> 为红色,所以渲染目标的纹理所处的背景为红色。</p>
<p>渲染目标可以用在各种各样的物体上。<a href="shadows.html">Shadows</a>用了渲染目标,<a href="picking.html">Picking can use a render target</a>,多种效果<a href="post-processing.html">post processing effects</a>需要用到渲染目标。
渲染汽车的后视镜,或者3D场景中的监控实时画面,都可能用到渲染目标。</p>
<p>关于 <a href="/docs/#api/zh/renderers/WebGLRenderTarget"><code class="notranslate" translate="no">WebGLRenderTarget</code></a> 的笔记。</p>
<ul>
<li><p>默认情况下 <a href="/docs/#api/zh/renderers/WebGLRenderTarget"><code class="notranslate" translate="no">WebGLRenderTarget</code></a> 会创建两个纹理。 颜色纹理和深度/模版纹理。如果你不需要深度或者模版纹理,你可以通过可选设置取消创建。例如:</p>
<pre class="prettyprint showlinemods notranslate lang-js" translate="no"> const rt = new THREE.WebGLRenderTarget(width, height, {
depthBuffer: false,
stencilBuffer: false,
});
</pre>
</li>
<li><p>你可能需要改变渲染目标的尺寸</p>
<p>在上面的例子,我们创建了固定尺寸512X512的渲染目标。对于像后处理,你通常需要创建跟画布一样尺寸的渲染目标。在我们的代码中意味着,当我们改变画布的尺寸,会同时更新渲染目标尺寸,和渲染目标中正在使用的摄像机。例如:</p>
<pre class="prettyprint showlinemods notranslate notranslate" translate="no">function render(time) {
time *= 0.001;
if (resizeRendererToDisplaySize(renderer)) {
const canvas = renderer.domElement;
camera.aspect = canvas.clientWidth / canvas.clientHeight;
camera.updateProjectionMatrix();
+ renderTarget.setSize(canvas.width, canvas.height);
+ rtCamera.aspect = camera.aspect;
+ rtCamera.updateProjectionMatrix();
}
</pre></li>
</ul>
</div>
</div>
</div>
<script src="/manual/resources/prettify.js"></script>
<script src="/manual/resources/lesson.js"></script>
</body></html>