What is Three.js?

Let's try to describe it briefly:
Three.js is a library that makes WebGL - 3D in the browser - easy to use. While a simple cube in raw WebGL would turn out hundreds of lines of Javascript and shader code, a Three.js equivalent is only a fraction of that.

Before we start

Before you can use Three.js, you need somewhere to display it. Save the following HTML to a file on your computer, along with a copy ofthree.min.js in the js/ directory, and open it in your browser.
<html> <head> <title>My first Three.js app</title> <style> body { margin: 0; } canvas { width: 100%; height: 100% } </style> </head> <body> <script src="js/three.min.js"></script> <script> // Our Javascript will go here. </script> </body> </html>
That's all. All the code below goes into the empty <script> tag.

Creating the scene

To actually be able to display anything with Three.js, we need three things: A scene, a camera, and a renderer so we can render the scene with the camera.
 var scene = new THREE.Scene(); var camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 0.1, 1000 ); var renderer = new THREE.WebGLRenderer(); renderer.setSize( window.innerWidth, window.innerHeight ); document.body.appendChild( renderer.domElement );
Let's take a moment to explain what's going on here. We have now set up the scene, our camera and the renderer. There are a few different cameras in Three.js. For now, let's use a PerspectiveCamera. The first attribute is the field of view.
The second one is the aspect ratio. You almost always want to use the width of the element divided by the height, or you'll get the same result as when you play old movies on a widescreen TV - the image looks squished.
The next two attributes are the near and far clipping plane. What that means, is that objects further away from the camera than the value of far or closer than near won't be rendered. You don't have to worry about this now, but you may want to use other values in your games to get better performance.
Next up is the renderer. This is where the magic happens. In addition to the WebGLRenderer we use here, Three.js comes with a few others, often used as fallbacks for users with older browsers or for those who don't have WebGL support for some reason.
In addition to creating the renderer instance, we also need to set the size at which we want it to render our app. It's a good idea to use the width and height of the area we want to fill with our game - in this case, the width and height of the browser window. For performance intensive games, you can also give setSize smaller values, like window.innerWidth/2 and window.innerHeight/2, for half the resolution. This does not mean that the game will only fill half the window, but rather look a bit blurry and scaled up.
Last but not least, we add the renderer element to our HTML document. This is a <canvas> element the renderer uses to display the scene to us.
"That's all good, but where's that cube you promised?" Let's add it now.

var geometry = new THREE.BoxGeometry( 1, 1, 1 ); var material = new THREE.MeshBasicMaterial( { color: 0x00ff00 } ); var cube = new THREE.Mesh( geometry, material ); scene.add( cube ); camera.position.z = 5;

To create a cube, we need a BoxGeometry. This is an object that contains all the points (vertices) and fill (faces) of the cube. We'll explore this more in the future.
In addition to the geometry, we need a material to color it. Three.js comes with several materials, but we'll stick to the MeshBasicMaterialfor now. All materials take an object of properties which will be applied to them. To keep things very simple, we only supply a color attribute of 0x00ff00, which is green. This works the same way that colors work in CSS or Photoshop (hex colors).
The third thing we need is a Mesh. A mesh is an object that takes a geometry, and applies a material to it, which we then can insert to our scene, and move freely around.
By default, when we call scene.add(), the thing we add will be added to the coordinates (0,0,0). This would cause both the camera and the cube to be inside each other. To avoid this, we simply move the camera out a bit.

Rendering the scene

If you copied the code from above into the HTML file we created earlier, you wouldn't be able to see anything. This is because we're not actually rendering anything yet. For that, we need what's called a render loop.

function render() { requestAnimationFrame( render ); renderer.render( scene, camera ); } render();

This will create a loop that causes the renderer to draw the scene 60 times per second. If you're new to writing games in the browser, you might say "why don't we just create a setInterval? The thing is - we could, but requestAnimationFrame has a number of advantages. Perhaps the most important one is that it pauses when the user navigates to another browser tab, hence not wasting their precious processing power and battery life.

Animating the cube

If you insert all the code above into the file you created before we began, you should see a green box. Let's make it all a little more interesting by rotating it.
Add the following right above the renderer.render call in your render function:
 cube.rotation.x += 0.1; cube.rotation.y += 0.1;
This will be run every frame (60 times per second), and give the cube a nice rotation animation. Basically, anything you want to move or change while the game / app is running has to go through the render loop. You can of course call other functions from there, so that you don't end up with a render function that's hundreds of lines.

The result

Congratulations! You have now completed your first Three.js application. It's simple, you have to start somewhere.
The full code is available below. Play around with it to get a better understanding of how it works.
 <html> <head> <title>My first Three.js app</title> <style> body { margin: 0; } canvas { width: 100%; height: 100% } </style> </head> <body> <script src="js/three.min.js"></script> <script> var scene = new THREE.Scene(); var camera = new THREE.PerspectiveCamera( 75, window.innerWidth/window.innerHeight, 0.1, 1000 ); var renderer = new THREE.WebGLRenderer(); renderer.setSize( window.innerWidth, window.innerHeight ); document.body.appendChild( renderer.domElement ); var geometry = new THREE.BoxGeometry( 1, 1, 1 ); var material = new THREE.MeshBasicMaterial( { color: 0x00ff00 } ); var cube = new THREE.Mesh( geometry, material ); scene.add( cube ); camera.position.z = 5; var render = function () { requestAnimationFrame( render ); cube.rotation.x += 0.1; cube.rotation.y += 0.1; renderer.render(scene, camera); }; render(); </script> </body> </html>

three.js 简介的更多相关文章

  1. prototype.js简介

    prototype.js简介 2007-11-21 14:22 prototype.js是一个很强大的Javascript函数库,它可以让你很轻松的使用一些特效,实现AJAX的功能.虽然prototy ...

  2. HTML基础--JS简介、基本语法、类型转换、变量、运算符、分支语句、循环语句、数组、函数、函数调用.avi

    JS简介 1.JavaScript是个什么东西? 它是个脚本语言,需要有宿主文件,它的宿主文件是HTML文件. 2.它与Java什么关系? 没有什么直接的联系,Java是Sun公司(已被Oracle收 ...

  3. 01 Node.js简介, 安装&配置

    Node.js 简介 Node.js 是什么 Node.js 有着强大而灵活的包管理器(node package manager,npm) 目前, 已经有强大第三方工具模块, 例如数据库连接, 网站开 ...

  4. Vue.js简介

    Vue.js简介 Vue.js的作者为Evan You(尤雨溪),任职于Google Creative Lab,虽然是Vue是一个个人项目,但在发展前景上个人认为绝不输于Google的AngularJ ...

  5. Gulp.js简介

    Gulp.js简介 我们讨论了很多关于怎么减少页面体积,提高重网站性能的方法.有些是操作是一劳永逸的,如开启服务器的gzip压缩,使用适当的图片格式,或删除一些不必要的字符.但有一些任务是每次工作都必 ...

  6. 《React Native 精解与实战》书籍连载「Node.js 简介与 React Native 开发环境配置」

    此文是我的出版书籍<React Native 精解与实战>连载分享,此书由机械工业出版社出版,书中详解了 React Native 框架底层原理.React Native 组件布局.组件与 ...

  7. vue学习（一）、Vue.js简介

    Vue.js 五天 汤小洋一. Vue.js简介1. Vue.js是什么Vue.js也称为Vue,读音/vju:/,类似view,错误读音v-u-e 版本:v1.0 v2.0 是一个构建用户界面的框架 ...

  8. JS 简介

    JS 简介 JavaScript 是世界上最流行的编程语言. 这门语言可用于 HTML 和 web,更可广泛用于服务器.PC.笔记本电脑.平板电脑和智能手机等设备. avaScript 是脚本语言 J ...

  9. Zepto.js简介

    Zepto.js简介 一.总结 一句话总结: Zepto.js语法和jquery起码百分之90相似,主要做移动端框架,和jquery mobile是一个类型的概念 1.Zepto.js做移动端的特点? ...

  10. 在electron中使用sqlite：sql.js简介

    在electron中使用sqlite:sql.js简介 在开发electron应用的时候如果想要使用sqlite3,步骤上除了npm安装以外还要rebuild,比较麻烦.如果你想找一个开箱即用的sql ...

随机推荐

  1. 将获得到的json赋值到下拉框

    $(function () { $.getJSON('handler/addEmployees.ashx', function (json) { alert(json.length); //遍历赋值 ...

  2. wire与reg的区别？转载大神！

    本文转自:http://www.cnblogs.com/thymon/archive/2010/06/09/1754541.html //------------------------------- ...

  3. IOS之UIView的tag学习

    tag是UIView的一个属性,而且要求tag值唯一.父视图可以通过tag来找到一个子视图 UIView *redView = [[UIView alloc]initWithFrame:CGRectM ...

  4. Android -- Drawable与Bitmap测试

    Drawable                                                                                 以下这个是测试加载10 ...

  5. 如何用pdfbox-app-1.8.10.jar批处理将pdf文档转换成text文档

    1.首先下载pdfbox-app-1.8.10.jar(下载地址:http://pdfbox.apache.org/download.html) 2.将pdfbox-app-1.8.10.jar加载到 ...

  6. websphere OSGi应用环境下服务调用saaj包加载问题分析报告

    websphere OSGi应用环境下服务调用saaj包加载问题分析报告 作者:bingjava 版权声明:本文为博主原创文章,转载请说明出处:http://www.cnblogs.com/bingj ...

  7. shell ulimit -n

    通过ulimit -n命令可以查看linux系统里打开文件描述符的最大值,一般缺省值是1024,

  8. 我对GIT的理解

    git是一个版本或项目代码管理工具.能够方便的管理多个开发人员共同协助开发的代码.在git的管理下,每个开发人员都能同时对项目进行开发,开发人员被划分成不同的分支,每个开发人员都能拥有自己的一个或者多 ...

  9. 将通过find命令找到的文件拷贝到一个新的目录中

    将通过find命令找到的文件拷贝到一个新的目录中 有这样的一个需求,需要将一部分符合条件的文件从一个目录拷贝到另一个目录中,我通过find命令从源目录查找到符合条件的文件然后使用cp命令拷贝到目标目录 ...

  10. ExtjsMVC开发过程中遇到的具体问题总结

    1.登陆相关问题 1.如何在文本框中增加提示信息             2.如何在文本框中触发回车事件             3.如何在回车事件中触发按钮的动作             总结:ht ...