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学习threejs，PerspectiveCamera透视相机和OrthographicCamera正交相机对比

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文章目录

一、🍀前言
- 1.1 ☘️THREE.PerspectiveCamera透视相机
- 1.2 ☘️THREE.OrthographicCamera正交相机
二、🍀PerspectiveCamera透视相机和OrthographicCamera正交相机对比
- 1. ☘️实现思路
- 2. ☘️代码样例

一、🍀前言

本文详细介绍如何基于threejs在三维场景中PerspectiveCamera透视相机和OrthographicCamera正交相机进行对比，亲测可用。希望能帮助到您。一起学习，加油！加油！

1.1 ☘️THREE.PerspectiveCamera透视相机

THREE.PerspectiveCamera这一投影模式被用来模拟人眼所看到的景象，它是3D场景的渲染中使用得最普遍的投影模式。
构造函数：
PerspectiveCamera( fov : Number, aspect : Number, near : Number, far : Number )
fov — 摄像机视锥体垂直视野角度
aspect — 摄像机视锥体长宽比
near — 摄像机视锥体近端面
far — 摄像机视锥体远端面
这些参数一起定义了摄像机的viewing frustum（视锥体）。
属性：
在这里插入图片描述
方法：

1.2 ☘️THREE.OrthographicCamera正交相机

THREE.OrthographicCamera正交相机在这种投影模式下，无论物体距离相机距离远或者近，在最终渲染的图片中物体的大小都保持不变。
这对于渲染2D场景或者UI元素是非常有用的。
构造函数：
OrthographicCamera( left : Number, right : Number, top : Number, bottom : Number, near : Number, far : Number )
left — 摄像机视锥体左侧面。
right — 摄像机视锥体右侧面。
top — 摄像机视锥体上侧面。
bottom — 摄像机视锥体下侧面。
near — 摄像机视锥体近端面。
far — 摄像机视锥体远端面。
这些参数一起定义了摄像机的viewing frustum（视锥体）。
属性：
在这里插入图片描述
方法：

二、🍀PerspectiveCamera透视相机和OrthographicCamera正交相机对比

1. ☘️实现思路

1、初始化renderer渲染器
2、初始化Scene三维场景scene。
3、初始化PerspectiveCamera透视相机camera，定义相机位置 camera.position。
4、初始化THREE.AmbientLight环境光源，scene场景加入环境光源。创建THREE.DirectionalLight平行光源directionalLight，设置平行光源位置，scene场景加入平行光源。
5、加载几何模型：创建THREE.PlaneGeometry平面几何体planeGeometry，创建THREE.MeshLambertMaterial漫反射材质planeMaterial，传入参数planeGeometry和planeMaterial创建平面几何体网格对象plane，设置plane投影，设置plane的位置和旋转角度，场景scene中加入plane。在plane上循环创建立方体网格对象cube，将plane铺满，具体代码参考代码样例。
6、加入gui控制，实现PerspectiveCamera透视相机和OrthographicCamera正交相机的切换，进行效果对比。加入stats监控器，监控帧数信息。

2. ☘️代码样例

<!DOCTYPE html><html><head><title>PerspectiveCamera透视相机和OrthographicCamera正交相机对比</title><script type="text/javascript" src="../libs/three.js"></script><script type="text/javascript" src="../libs/stats.js"></script><script type="text/javascript" src="../libs/dat.gui.js"></script><style>body {/* set margin to 0 and overflow to hidden, to go fullscreen */margin: 0;overflow: hidden;}</style>
</head>
<body><div id="Stats-output">
</div>
<!-- Div which will hold the Output -->
<div id="WebGL-output">
</div><!-- Javascript code that runs our Three.js examples -->
<script type="text/javascript">// once everything is loaded, we run our Three.js stuff.function init() {var stats = initStats();// create a scene, that will hold all our elements such as objects, cameras and lights.var scene = new THREE.Scene();// create a camera, which defines where we're looking at.var camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 1000);camera.position.x = 120;camera.position.y = 60;camera.position.z = 180;// create a render and set the sizevar renderer = new THREE.WebGLRenderer();renderer.setClearColor(new THREE.Color(0xEEEEEE, 1.0));renderer.setSize(window.innerWidth, window.innerHeight);// create the ground planevar planeGeometry = new THREE.PlaneGeometry(180, 180);var planeMaterial = new THREE.MeshLambertMaterial({color: 0xffffff});var plane = new THREE.Mesh(planeGeometry, planeMaterial);// rotate and position the planeplane.rotation.x = -0.5 * Math.PI;plane.position.x = 0;plane.position.y = 0;plane.position.z = 0;// add the plane to the scenescene.add(plane);var cubeGeometry = new THREE.BoxGeometry(4, 4, 4);for (var j = 0; j < (planeGeometry.parameters.height / 5); j++) {for (var i = 0; i < planeGeometry.parameters.width / 5; i++) {var rnd = Math.random() * 0.75 + 0.25;var cubeMaterial = new THREE.MeshLambertMaterial();cubeMaterial.color = new THREE.Color(rnd, 0, 0);var cube = new THREE.Mesh(cubeGeometry, cubeMaterial);cube.position.z = -((planeGeometry.parameters.height) / 2) + 2 + (j * 5);cube.position.x = -((planeGeometry.parameters.width) / 2) + 2 + (i * 5);cube.position.y = 2;scene.add(cube);}}var directionalLight = new THREE.DirectionalLight(0xffffff, 0.7);directionalLight.position.set(-20, 40, 60);scene.add(directionalLight);// add subtle ambient lightingvar ambientLight = new THREE.AmbientLight(0x292929);scene.add(ambientLight);// add the output of the renderer to the html elementdocument.getElementById("WebGL-output").appendChild(renderer.domElement);// call the render functionvar step = 0;var controls = new function () {this.perspective = "Perspective";this.switchCamera = function () {if (camera instanceof THREE.PerspectiveCamera) {camera = new THREE.OrthographicCamera(window.innerWidth / -16, window.innerWidth / 16, window.innerHeight / 16, window.innerHeight / -16, -200, 500);camera.position.x = 120;camera.position.y = 60;camera.position.z = 180;camera.lookAt(scene.position);this.perspective = "Orthographic";} else {camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 1000);camera.position.x = 120;camera.position.y = 60;camera.position.z = 180;camera.lookAt(scene.position);this.perspective = "Perspective";}};};var gui = new dat.GUI();gui.add(controls, 'switchCamera');gui.add(controls, 'perspective').listen();// make sure that for the first time, the// camera is looking at the scenecamera.lookAt(scene.position);render();function render() {stats.update();// render using requestAnimationFramerequestAnimationFrame(render);renderer.render(scene, camera);}function initStats() {var stats = new Stats();stats.setMode(0); // 0: fps, 1: ms// Align top-leftstats.domElement.style.position = 'absolute';stats.domElement.style.left = '0px';stats.domElement.style.top = '0px';document.getElementById("Stats-output").appendChild(stats.domElement);return stats;}}window.onload = init</script>
</body>
</html>