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<!DOCTYPE html><html lang="zh"><head>
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<title>摄像机</title>
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{
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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>摄像机</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>本文是关于 three.js 系列文章的一部分。第一篇文章是 <a href="fundamentals.html">three.js 基础</a>。如果你还没看过而且对three.js 还不熟悉，那应该从那里开始，并且了解如何<a href="setup.html">设置开发环境</a>。上一篇文章介绍了 three.js 中的 <a href="textures.html">纹理</a>。</p>
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<p>我们开始谈谈three.js中的摄像机. 我们已经在<a href="fundamentals.html">第一篇文章</a> 中涉及到了摄像机的一些知识，这里我们要更深入一些. </p>
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<p>在three.js中最常用的摄像机并且之前我们一直用的摄像机是<code class="notranslate" translate="no">透视摄像机 PerspectiveCamera</code>，它可以提供一个近大远小的3D视觉效果. </p>
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<p><a href="/docs/#api/zh/cameras/PerspectiveCamera"><code class="notranslate" translate="no">PerspectiveCamera</code></a> 定义了一个 <em>视锥（frustum）</em>。<a href="https://en.wikipedia.org/wiki/Frustum"><em>frustum</em> 是一个切掉顶的三角锥或者说实心金字塔型</a>。
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说到<em>实心体solid</em>，在这里通常是指一个立方体、一个圆锥、一个球、一个圆柱或锥台。</p>
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<div class="spread">
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<div><div data-diagram="shapeCube"></div><div>立方体</div></div>
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<div><div data-diagram="shapeCone"></div><div>圆锥</div></div>
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<div><div data-diagram="shapeSphere"></div><div>球</div></div>
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<div><div data-diagram="shapeCylinder"></div><div>圆柱</div></div>
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<div><div data-diagram="shapeFrustum"></div><div>锥台</div></div>
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</div>
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<p>重新讲一遍这些东西是因为我好久没有在意过了。很多书或者文章提到<em>锥台</em>这个东西的时候我扫一眼就过去了。再了解一下不同几何体会让下面的一些表述变得更为感性...吧😅</p>
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<p><a href="/docs/#api/zh/cameras/PerspectiveCamera"><code class="notranslate" translate="no">PerspectiveCamera</code></a>通过四个属性来定义一个视锥。<code class="notranslate" translate="no">near</code>定义了视锥的前端，<code class="notranslate" translate="no">far</code>定义了后端，<code class="notranslate" translate="no">fov</code>是视野，通过计算正确的高度来从摄像机的位置获得指定的以<code class="notranslate" translate="no">near</code>为单位的视野，定义的是视锥的前端和后端的高度。<code class="notranslate" translate="no">aspect</code>间接地定义了视锥前端和后端的宽度，实际上视锥的宽度是通过高度乘以 aspect 来得到的。</p>
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<p><img src="../resources/frustum-3d.svg" width="500" class="threejs_center"></p>
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<p>我们借用<a href="lights.html">上一篇文章</a>的场景. 其中包含一个地平面，一个球和一个立方体，我们可以在其中调整摄像机的设置。
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我们通过<code class="notranslate" translate="no">MinMaxGUIHelper</code>来调整<code class="notranslate" translate="no">near</code>，<code class="notranslate" translate="no">far</code>的设置。显然<code class="notranslate" translate="no">near</code>应该总是比<code class="notranslate" translate="no">far</code>要小。lil-gui 有<code class="notranslate" translate="no">min</code>和<code class="notranslate" translate="no">max</code>两个属性可调，然后这两个属性将决定摄像机的设置。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">class MinMaxGUIHelper {
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constructor(obj, minProp, maxProp, minDif) {
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this.obj = obj;
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this.minProp = minProp;
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this.maxProp = maxProp;
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this.minDif = minDif;
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}
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get min() {
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return this.obj[this.minProp];
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}
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set min(v) {
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this.obj[this.minProp] = v;
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this.obj[this.maxProp] = Math.max(this.obj[this.maxProp], v + this.minDif);
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}
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get max() {
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return this.obj[this.maxProp];
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}
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set max(v) {
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this.obj[this.maxProp] = v;
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this.min = this.min; // 这将调用min的setter
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}
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}
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</pre>
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<p>现在我们可以将GUI设置为：</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">function updateCamera() {
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camera.updateProjectionMatrix();
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}
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const gui = new GUI();
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gui.add(camera, 'fov', 1, 180).onChange(updateCamera);
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const minMaxGUIHelper = new MinMaxGUIHelper(camera, 'near', 'far', 0.1);
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gui.add(minMaxGUIHelper, 'min', 0.1, 50, 0.1).name('near').onChange(updateCamera);
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gui.add(minMaxGUIHelper, 'max', 0.1, 50, 0.1).name('far').onChange(updateCamera);
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</pre>
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<p>任何时候摄像机的设置变动，我们需要调用摄像机的<a href="/docs/#api/zh/cameras/PerspectiveCamera#updateProjectionMatrix"><code class="notranslate" translate="no">updateProjectionMatrix</code></a>来更新设置。我们写一个函数<code class="notranslate" translate="no">updataCamera</code>，当lil-gui改变了属性的时候会调用它来更新参数。</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/cameras-perspective.html"></iframe></div>
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<a class="threejs_center" href="/manual/examples/cameras-perspective.html" target="_blank">点击此处在新标签页中打开</a>
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</div>
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<p></p>
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<p>现在可以调整这些数值来观察这些参数是如何影响摄像机的。注意我们并没有改变<code class="notranslate" translate="no">aspect</code>，因为这个参数来自于窗口的大小. 如果想调整<code class="notranslate" translate="no">aspect</code>，只需要开个新窗口然后调整窗口大小就可以了。</p>
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<p>即便是这样，观察参数对视野的影响还是挺麻烦的. 所以我们来设置两台摄像机吧! 一台是跟上面一样展现出摄像机中看到的实际场景，另一个则是用来观察这个实际工作的摄像机，然后画出摄像机的视锥. </p>
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<p>我们需要用到three.js的剪函数(scissor function)来画两个场景和两个摄像机. </p>
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<p>首先让我们用HTML和CSS来定义两个肩并肩的元素. 这也将帮助我们将两个摄像机赋予不同的<a href="/docs/#examples/controls/OrbitControls"><code class="notranslate" translate="no">OrbitControls</code></a>。</p>
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<pre class="prettyprint showlinemods notranslate lang-html" translate="no"><body>
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<canvas id="c"></canvas>
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+ <div class="split">
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+ <div id="view1" tabindex="1"></div>
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+ <div id="view2" tabindex="2"></div>
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+ </div>
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</body>
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</pre>
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<p>CSS将控制两个视窗并排显示在 canvas 中：</p>
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<pre class="prettyprint showlinemods notranslate lang-css" translate="no">.split {
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position: absolute;
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left: 0;
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top: 0;
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width: 100%;
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height: 100%;
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display: flex;
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}
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.split>div {
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width: 100%;
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height: 100%;
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}
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</pre>
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<p>接下来将添加一个<a href="/docs/#api/zh/helpers/CameraHelper"><code class="notranslate" translate="no">CameraHelper</code></a>, 它可以把摄像机的视锥画出来：</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const cameraHelper = new THREE.CameraHelper(camera);
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...
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scene.add(cameraHelper);
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</pre>
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<p>我们现在需要查找到刚刚定义的两个元素：</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const view1Elem = document.querySelector('#view1');
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const view2Elem = document.querySelector('#view2');
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</pre>
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<p>现在只给第一个视窗中的摄像机分配<a href="/docs/#examples/controls/OrbitControls"><code class="notranslate" translate="no">OrbitControls</code></a>：</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">-const controls = new OrbitControls(camera, canvas);
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+const controls = new OrbitControls(camera, view1Elem);
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</pre>
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<p>我们定义第二个<a href="/docs/#api/zh/cameras/PerspectiveCamera"><code class="notranslate" translate="no">PerspectiveCamera</code></a>和<a href="/docs/#examples/controls/OrbitControls"><code class="notranslate" translate="no">OrbitControls</code></a>：</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const camera2 = new THREE.PerspectiveCamera(
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60, // fov
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2, // aspect
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0.1, // near
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500, // far
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);
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camera2.position.set(40, 10, 30);
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camera2.lookAt(0, 5, 0);
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const controls2 = new OrbitControls(camera2, view2Elem);
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controls2.target.set(0, 5, 0);
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controls2.update();
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</pre>
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<p>最后，我们需要使用剪刀功能从每个摄影机的视角渲染场景，以仅渲染画布的一部分。
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这个函数接受一个元素，计算这个元素在canvas上的重叠面积，这将设置剪刀函数和视角长宽并返回 aspect ：</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">function setScissorForElement(elem) {
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const canvasRect = canvas.getBoundingClientRect();
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const elemRect = elem.getBoundingClientRect();
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// 计算canvas的尺寸
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const right = Math.min(elemRect.right, canvasRect.right) - canvasRect.left;
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const left = Math.max(0, elemRect.left - canvasRect.left);
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const bottom = Math.min(elemRect.bottom, canvasRect.bottom) - canvasRect.top;
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const top = Math.max(0, elemRect.top - canvasRect.top);
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const width = Math.min(canvasRect.width, right - left);
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const height = Math.min(canvasRect.height, bottom - top);
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// 设置剪函数以仅渲染一部分场景
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const positiveYUpBottom = canvasRect.height - bottom;
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renderer.setScissor(left, positiveYUpBottom, width, height);
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renderer.setViewport(left, positiveYUpBottom, width, height);
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// 返回aspect
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return width / height;
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}
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</pre>
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<p>我们用这个函数在<code class="notranslate" translate="no">render</code>中绘制两遍场景</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no"> function render() {
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- if (resizeRendererToDisplaySize(renderer)) {
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- const canvas = renderer.domElement;
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- camera.aspect = canvas.clientWidth / canvas.clientHeight;
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- camera.updateProjectionMatrix();
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- }
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+ resizeRendererToDisplaySize(renderer);
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+
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+ // 启用剪刀函数
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+ renderer.setScissorTest(true);
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+
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+ // 渲染主视野
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+ {
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+ const aspect = setScissorForElement(view1Elem);
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+
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+ // 用计算出的aspect修改摄像机参数
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+ camera.aspect = aspect;
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+ camera.updateProjectionMatrix();
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+ cameraHelper.update();
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+
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+ // 来原视野中不要绘制cameraHelper
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+ cameraHelper.visible = false;
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+
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+ scene.background.set(0x000000);
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+
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+ // 渲染
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+ renderer.render(scene, camera);
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+ }
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+
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+ // 渲染第二台摄像机
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+ {
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+ const aspect = setScissorForElement(view2Elem);
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+
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+ // 调整aspect
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+ camera2.aspect = aspect;
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+ camera2.updateProjectionMatrix();
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+
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+ // 在第二台摄像机中绘制cameraHelper
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+ cameraHelper.visible = true;
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+
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+ scene.background.set(0x000040);
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+
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+ renderer.render(scene, camera2);
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+ }
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- renderer.render(scene, camera);
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requestAnimationFrame(render);
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}
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requestAnimationFrame(render);
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}
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</pre>
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<p>上面的代码还将主辅摄像机的背景色区分开以利观察。</p>
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<p>我们可以移除<code class="notranslate" translate="no">updateCamera</code>了，因为所有的东西在<code class="notranslate" translate="no">render</code>中更新过了。</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">-function updateCamera() {
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- camera.updateProjectionMatrix();
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-}
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const gui = new GUI();
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-gui.add(camera, 'fov', 1, 180).onChange(updateCamera);
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+gui.add(camera, 'fov', 1, 180);
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const minMaxGUIHelper = new MinMaxGUIHelper(camera, 'near', 'far', 0.1);
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-gui.add(minMaxGUIHelper, 'min', 0.1, 50, 0.1).name('near').onChange(updateCamera);
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-gui.add(minMaxGUIHelper, 'max', 0.1, 50, 0.1).name('far').onChange(updateCamera);
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+gui.add(minMaxGUIHelper, 'min', 0.1, 50, 0.1).name('near');
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+gui.add(minMaxGUIHelper, 'max', 0.1, 50, 0.1).name('far');
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</pre>
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<p>现在我们就可以在辅摄像机中观察到主摄像机的视锥轮廓了。</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/cameras-perspective-2-scenes.html"></iframe></div>
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<a class="threejs_center" href="/manual/examples/cameras-perspective-2-scenes.html" target="_blank">点击此处在新标签页中打开</a>
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</div>
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<p></p>
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<p>左侧可以看到主摄像机的视角，右侧则是辅摄像机观察主摄像机和主摄像机的视锥轮廓。可以调整<code class="notranslate" translate="no">near</code>，<code class="notranslate" translate="no">far</code>，<code class="notranslate" translate="no">fov</code>和用鼠标移动摄像机来观察视锥轮廓和场景之间的关系. </p>
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<p>将<code class="notranslate" translate="no">near</code>调整到大概20左右，前景就会在视锥中消失。<code class="notranslate" translate="no">far</code>低于35时，远景也不复存在. </p>
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<p>这带来一个问题，为什么不把<code class="notranslate" translate="no">near</code>设置到0.0000000001然后将<code class="notranslate" translate="no">far</code>设置成100000000，使得一切都可以尽收眼底? 原因是你的GPU没有足够的精度来决定某个东西是另一个东西的前面还是后面。更糟的是，在默认情况下，离摄像机近的将会更清晰，离摄像机远的模糊，从<code class="notranslate" translate="no">near</code>到<code class="notranslate" translate="no">far</code>逐渐过渡。</p>
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<p>从上面的例子出发，我们向场景中添加20个球：</p>
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<pre class="prettyprint showlinemods notranslate lang-js" translate="no">{
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const sphereRadius = 3;
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const sphereWidthDivisions = 32;
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const sphereHeightDivisions = 16;
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const sphereGeo = new THREE.SphereGeometry(sphereRadius, sphereWidthDivisions, sphereHeightDivisions);
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const numSpheres = 20;
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for (let i = 0; i < numSpheres; ++i) {
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const sphereMat = new THREE.MeshPhongMaterial();
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sphereMat.color.setHSL(i * .73, 1, 0.5);
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const mesh = new THREE.Mesh(sphereGeo, sphereMat);
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mesh.position.set(-sphereRadius - 1, sphereRadius + 2, i * sphereRadius * -2.2);
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scene.add(mesh);
|
|
|
}
|
|
|
}
|
|
|
</pre>
|
|
|
<p>把 <code class="notranslate" translate="no">near</code> 设置成0.00001</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const fov = 45;
|
|
|
const aspect = 2; // canvas 默认
|
|
|
-const near = 0.1;
|
|
|
+const near = 0.00001;
|
|
|
const far = 100;
|
|
|
const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
|
|
|
</pre>
|
|
|
<p>调整一下GUI使得能设置到0.00001</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">-gui.add(minMaxGUIHelper, 'min', 0.1, 50, 0.1).name('near').onChange(updateCamera);
|
|
|
+gui.add(minMaxGUIHelper, 'min', 0.00001, 50, 0.00001).name('near').onChange(updateCamera);
|
|
|
</pre>
|
|
|
<p>你觉得会发生什么？</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/cameras-z-fighting.html"></iframe></div>
|
|
|
<a class="threejs_center" href="/manual/examples/cameras-z-fighting.html" target="_blank">点击此处在新标签页中打开</a>
|
|
|
</div>
|
|
|
|
|
|
<p></p>
|
|
|
<p>这就是一个典型的<em>z冲突</em>的例子。GPU没有足够的精度来决定哪个像素在前哪个在后。</p>
|
|
|
<p>如果你的机器太好可能不会出现我说的情况，我把我看到的截图放在这：</p>
|
|
|
<div class="threejs_center"><img src="../resources/images/z-fighting.png" style="width: 570px;"></div>
|
|
|
|
|
|
<p>解决的方法之一是告诉three.js使用不同的方法计算像素的前后关系。我们可以在创建<a href="/docs/#api/zh/renderers/WebGLRenderer"><code class="notranslate" translate="no">WebGLRenderer</code></a>时开启<code class="notranslate" translate="no">logarithmicDepthBuffer</code>。</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">-const renderer = new THREE.WebGLRenderer({antialias: true, canvas});
|
|
|
+const renderer = new THREE.WebGLRenderer({
|
|
|
+ antialias: true,
|
|
|
+ canvas,
|
|
|
+ logarithmicDepthBuffer: true,
|
|
|
+});
|
|
|
</pre>
|
|
|
<p>这看起来就行了</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/cameras-logarithmic-depth-buffer.html"></iframe></div>
|
|
|
<a class="threejs_center" href="/manual/examples/cameras-logarithmic-depth-buffer.html" target="_blank">点击此处在新标签页中打开</a>
|
|
|
</div>
|
|
|
|
|
|
<p></p>
|
|
|
<p>如果上面的方案不行的话，那你就遇到了<em>为什么不能无脑使用这种解决方案</em>的情况了。截止2018年9月，绝大多数台式机可以，但几乎没有移动设备支持这个功能。</p>
|
|
|
<p>另外，最好别用这种解决方案，因为这会大大降低运行速度。</p>
|
|
|
<p>即便是现在跑得好好地，选择太小的<code class="notranslate" translate="no">near</code>和太大的<code class="notranslate" translate="no">far</code>最终也会遇到同样的问题。</p>
|
|
|
<p>所以说你需要选择好好抉择<code class="notranslate" translate="no">near</code>和<code class="notranslate" translate="no">far</code>的设置，来和你的场景配合。既不丢失重要的近景，也不让远处的东西消失不见。如果你想渲染一个巨大的场景，不但能看清面前的人的眼睫毛又想看到50公里以外的玩意，你得自己想一个<em>厉害的</em>方案，这里就不涉及了。现在，好好地选个适合的参数就行。</p>
|
|
|
<p>第二种常见的摄像机是<code class="notranslate" translate="no">正交摄像机 OrthographicCamera</code>，和指定一个视锥不同的是，它需要设置<code class="notranslate" translate="no">left</code>，<code class="notranslate" translate="no">right</code>
|
|
|
<code class="notranslate" translate="no">top</code>，<code class="notranslate" translate="no">bottom</code>，<code class="notranslate" translate="no">near</code>，和<code class="notranslate" translate="no">far</code>指定一个长方体，使得视野是平行的而不是透视的。</p>
|
|
|
<p>我们来把上面的例子改成<a href="/docs/#api/zh/cameras/OrthographicCamera"><code class="notranslate" translate="no">OrthographicCamera</code></a>, 首先来设置摄像机</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const left = -1;
|
|
|
const right = 1;
|
|
|
const top = 1;
|
|
|
const bottom = -1;
|
|
|
const near = 5;
|
|
|
const far = 50;
|
|
|
const camera = new THREE.OrthographicCamera(left, right, top, bottom, near, far);
|
|
|
camera.zoom = 0.2;
|
|
|
</pre>
|
|
|
<p>我们将<code class="notranslate" translate="no">left</code>和<code class="notranslate" translate="no">bottom</code>设置成 -1 <code class="notranslate" translate="no">right</code> 和 <code class="notranslate" translate="no">top</code>设成 1，这样就使盒子宽为两个单位，高两个单位。我们接下来通过调整<code class="notranslate" translate="no">left</code>和<code class="notranslate" translate="no">top</code>来选择其 aspect 。我们将用<code class="notranslate" translate="no">zoom</code>属性来调整相机到底展现多少的单位大小。</p>
|
|
|
<p>给GUI添加<code class="notranslate" translate="no">zoom</code>设置：</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const gui = new GUI();
|
|
|
+gui.add(camera, 'zoom', 0.01, 1, 0.01).listen();
|
|
|
</pre>
|
|
|
<p><code class="notranslate" translate="no">listen</code>调用告诉lil-gui去监视属性的变化。写在这里是因为<a href="/docs/#examples/controls/OrbitControls"><code class="notranslate" translate="no">OrbitControls</code></a>同样可以控制缩放。在这个例子中，鼠标滚轮将会通过<a href="/docs/#examples/controls/OrbitControls"><code class="notranslate" translate="no">OrbitControls</code></a>控件来控制缩放。</p>
|
|
|
<p>最后更改aspect然后更新摄像机：</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">{
|
|
|
const aspect = setScissorForElement(view1Elem);
|
|
|
|
|
|
// 使用aspect更新摄像机
|
|
|
- camera.aspect = aspect;
|
|
|
+ camera.left = -aspect;
|
|
|
+ camera.right = aspect;
|
|
|
camera.updateProjectionMatrix();
|
|
|
cameraHelper.update();
|
|
|
|
|
|
// 在主摄像机中不绘制视野辅助线
|
|
|
cameraHelper.visible = false;
|
|
|
|
|
|
scene.background.set(0x000000);
|
|
|
renderer.render(scene, camera);
|
|
|
}
|
|
|
</pre>
|
|
|
<p>现在就可以看到<a href="/docs/#api/zh/cameras/OrthographicCamera"><code class="notranslate" translate="no">OrthographicCamera</code></a>工作了。</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/cameras-orthographic-2-scenes.html"></iframe></div>
|
|
|
<a class="threejs_center" href="/manual/examples/cameras-orthographic-2-scenes.html" target="_blank">点击此处在新标签页中打开</a>
|
|
|
</div>
|
|
|
|
|
|
<p></p>
|
|
|
<p>大多数情况下，绘制2D图像的时候会用到<a href="/docs/#api/zh/cameras/OrthographicCamera"><code class="notranslate" translate="no">OrthographicCamera</code></a>。你可以自己决定摄像机的视野大小。比如说你想让 canvas 的一个像素匹配摄像机的一个单位，你可以这么做：</p>
|
|
|
<p>将原点置于中心，令一个像素等于一个单位</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">camera.left = -canvas.width / 2;
|
|
|
camera.right = canvas.width / 2;
|
|
|
camera.top = canvas.height / 2;
|
|
|
camera.bottom = -canvas.height / 2;
|
|
|
camera.near = -1;
|
|
|
camera.far = 1;
|
|
|
camera.zoom = 1;
|
|
|
</pre>
|
|
|
<p>或者如果我们想让原点在左上，就像是2D canvas</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">camera.left = 0;
|
|
|
camera.right = canvas.width;
|
|
|
camera.top = 0;
|
|
|
camera.bottom = canvas.height;
|
|
|
camera.near = -1;
|
|
|
camera.far = 1;
|
|
|
camera.zoom = 1;
|
|
|
</pre>
|
|
|
<p>这样左上角就成了0,0</p>
|
|
|
<p>试试，这样设置摄像机</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const left = 0;
|
|
|
const right = 300; // 默认的canvas大小
|
|
|
const top = 0;
|
|
|
const bottom = 150; // 默认的canvas大小
|
|
|
const near = -1;
|
|
|
const far = 1;
|
|
|
const camera = new THREE.OrthographicCamera(left, right, top, bottom, near, far);
|
|
|
camera.zoom = 1;
|
|
|
</pre>
|
|
|
<p>然后我们载入六个材质，生成六个平面，一一对应。把每一个平面绑定到父对象<a href="/docs/#api/zh/core/Object3D"><code class="notranslate" translate="no">THREE.Object3D</code></a>上，以便调整每个平面和左上角原点的相对关系</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">const loader = new THREE.TextureLoader();
|
|
|
const textures = [
|
|
|
loader.load('resources/images/flower-1.jpg'),
|
|
|
loader.load('resources/images/flower-2.jpg'),
|
|
|
loader.load('resources/images/flower-3.jpg'),
|
|
|
loader.load('resources/images/flower-4.jpg'),
|
|
|
loader.load('resources/images/flower-5.jpg'),
|
|
|
loader.load('resources/images/flower-6.jpg'),
|
|
|
];
|
|
|
const planeSize = 256;
|
|
|
const planeGeo = new THREE.PlaneGeometry(planeSize, planeSize);
|
|
|
const planes = textures.map((texture) => {
|
|
|
const planePivot = new THREE.Object3D();
|
|
|
scene.add(planePivot);
|
|
|
texture.magFilter = THREE.NearestFilter;
|
|
|
const planeMat = new THREE.MeshBasicMaterial({
|
|
|
map: texture,
|
|
|
side: THREE.DoubleSide,
|
|
|
});
|
|
|
const mesh = new THREE.Mesh(planeGeo, planeMat);
|
|
|
planePivot.add(mesh);
|
|
|
// 调整平面使得左上角为原点
|
|
|
mesh.position.set(planeSize / 2, planeSize / 2, 0);
|
|
|
return planePivot;
|
|
|
});
|
|
|
</pre>
|
|
|
<p>然后当 canvas 更新后我们更新摄像机设置</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">function render() {
|
|
|
|
|
|
if (resizeRendererToDisplaySize(renderer)) {
|
|
|
camera.right = canvas.width;
|
|
|
camera.bottom = canvas.height;
|
|
|
camera.updateProjectionMatrix();
|
|
|
}
|
|
|
|
|
|
...
|
|
|
</pre>
|
|
|
<p><code class="notranslate" translate="no">planes</code>是<a href="/docs/#api/zh/objects/Mesh"><code class="notranslate" translate="no">THREE.Mesh</code></a>的数组，每一个对应一个平面。
|
|
|
现在让它随着时间移动</p>
|
|
|
<pre class="prettyprint showlinemods notranslate lang-js" translate="no">function render(time) {
|
|
|
time *= 0.001; // 转换为秒;
|
|
|
|
|
|
...
|
|
|
|
|
|
const distAcross = Math.max(20, canvas.width - planeSize);
|
|
|
const distDown = Math.max(20, canvas.height - planeSize);
|
|
|
|
|
|
// 来回运动的总距离
|
|
|
const xRange = distAcross * 2;
|
|
|
const yRange = distDown * 2;
|
|
|
const speed = 180;
|
|
|
|
|
|
planes.forEach((plane, ndx) => {
|
|
|
// 为每个平面单独计算时间
|
|
|
const t = time * speed + ndx * 300;
|
|
|
|
|
|
// 在0到最远距离之间获取一个值
|
|
|
const xt = t % xRange;
|
|
|
const yt = t % yRange;
|
|
|
|
|
|
// 0到距离的一半, 向前运动
|
|
|
// 另一半的时候往回运动
|
|
|
const x = xt < distAcross ? xt : xRange - xt;
|
|
|
const y = yt < distDown ? yt : yRange - yt;
|
|
|
|
|
|
plane.position.set(x, y, 0);
|
|
|
});
|
|
|
|
|
|
renderer.render(scene, camera);
|
|
|
</pre>
|
|
|
<p>你可以看到图片在其中弹跳，和边际完美契合，就是2D canvas的效果一样</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/cameras-orthographic-canvas-top-left-origin.html"></iframe></div>
|
|
|
<a class="threejs_center" href="/manual/examples/cameras-orthographic-canvas-top-left-origin.html" target="_blank">点击此处在新标签页中打开</a>
|
|
|
</div>
|
|
|
|
|
|
<p></p>
|
|
|
<p>另一个常见的用途是用<a href="/docs/#api/zh/cameras/OrthographicCamera"><code class="notranslate" translate="no">OrthographicCamera</code></a>来展示模型的三视图。</p>
|
|
|
<div class="threejs_center"><img src="../resources/images/quad-viewport.png" style="width: 574px;"></div>
|
|
|
|
|
|
<p>上面的截图展示了一个透视图和三个正交视角。</p>
|
|
|
<p>这就是摄像机的基础. 我们在其他的文章中会介绍另外的一些摄像机用法。现在，我们移步到<a href="shadows.html">阴影</a>。</p>
|
|
|
<p><canvas id="c"></canvas></p>
|
|
|
<script type="module" src="../resources/threejs-cameras.js"></script>
|
|
|
|
|
|
</div>
|
|
|
</div>
|
|
|
</div>
|
|
|
|
|
|
<script src="../resources/prettify.js"></script>
|
|
|
<script src="../resources/lesson.js"></script>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
</body></html>
|