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

news2024/12/28 10:49:17

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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 size
        var renderer = new THREE.WebGLRenderer();

        renderer.setClearColor(new THREE.Color(0xEEEEEE, 1.0));
        renderer.setSize(window.innerWidth, window.innerHeight);

        // create the ground plane
        var planeGeometry = new THREE.PlaneGeometry(180, 180);
        var planeMaterial = new THREE.MeshLambertMaterial({color: 0xffffff});
        var plane = new THREE.Mesh(planeGeometry, planeMaterial);


        // rotate and position the plane
        plane.rotation.x = -0.5 * Math.PI;
        plane.position.x = 0;
        plane.position.y = 0;
        plane.position.z = 0;

        // add the plane to the scene
        scene.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 lighting
        var ambientLight = new THREE.AmbientLight(0x292929);
        scene.add(ambientLight);

        // add the output of the renderer to the html element
        document.getElementById("WebGL-output").appendChild(renderer.domElement);

        // call the render function
        var 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 scene
        camera.lookAt(scene.position);
        render();

        function render() {

            stats.update();
            // render using requestAnimationFrame
            requestAnimationFrame(render);
            renderer.render(scene, camera);
        }

        function initStats() {

            var stats = new Stats();

            stats.setMode(0); // 0: fps, 1: ms

            // Align top-left
            stats.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>