该示例主要是在正投影视觉下，使用 CSS3DRenderer 渲染基于CSS的3D对象，在3D场景中展示使用div绘制的几何图形。下面将会对该示例涉及到的一些知识点进行讲解。
一、 几个知识点
1. OrthographicCamera正投影机
在three.js 相机可以分为两种，OrthographicCamera正投影机 和 PerspectiveCamera 透视投影相机。在大多数项目中，我们都是使用投影相机，因为投影相机可以模拟人眼看物体是远小近大的规律。假如不需要远小近大，则可以采用正投影相机。
使用示例：
js
// 构造函数格式
OrthographicCamera( left, right, top, bottom, near, far )参数说明：
| 参数（属性） | 含义 |
|---|---|
| left | 渲染空间的左边界 |
| right | 渲染空间的右边界 |
| top | 渲染空间的上边界 |
| bottom | 渲染空间的下边界 |
| near | near 属性表示的是从距离相机多远的位置开始渲染，一般情况下会设置一个很小的值。默认值 0.1 |
| far | far 属性表示的是距离相机多远的位置截止渲染。如果设置的值偏小，会有部分场景看不到。默认值 2000 |
2. 欧拉Euler
构造函数：Euler(x,y,z,order)
参数xyz分别表示绕xyz轴旋转的角度值，角度单位是弧度。参数order表示旋转顺序,默认值XYZ，也可以设置为YXZ、YZX等值
javascript
// 创建一个欧拉对象，表示绕着xyz轴分别旋转45度，0度，90度
var Euler = new THREE.Euler( Math.PI/4,0, Math.PI/2);另一种形式设置：
ini
var Euler = new THREE.Euler();
Euler.x = Math.PI/4;
Euler.y = Math.PI/2;
Euler.z = Math.PI/4;注意： 模型的角度属性 .rotation 和 四元数属性 .quaternion 都是表示模型的角度状态，只是表达方式不同。 .rotation 属性值是欧拉对象 Euler, .quaternion 属性值是四元数对象 Quaternion
3. CSS3DRenderer
CSS3DRenderer 可以实现dom元素的3D效果，本质是把原来三维场景中的视图矩阵、模型矩阵、投影矩阵的变换，通过 css 中的 translateZ、matrix3d、perspective等属性模拟出来并作用在DOOM上。
示例中通过createPlane()生成的div对象，需要使用CSS3DRenderer才能显示出来。
4. lil-gui 库使用，方便对场景参数进行可视化调整。该库的具体使用，可查阅其官网：
二、 完整示例
js
<!DOCTYPE html>
<html>
<head>
<title>three.js css3d - orthographic</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
<link type="text/css" rel="stylesheet" href="main.css">
<style>
body {
background-color: #f0f0f0;
}
a {
color: #f00;
}
#info {
color: #000000;
}
</style>
</head>
<body>
<div id="info"><a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> css3d - orthographic</div>
<script type="importmap">
{
"imports": {
"three": "../build/three.module.js",
"three/addons/": "./jsm/"
}
}
</script>
<script type="module">
import * as THREE from 'three';
import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
import { CSS3DRenderer, CSS3DObject } from 'three/addons/renderers/CSS3DRenderer.js';
import { GUI } from 'three/addons/libs/lil-gui.module.min.js';
let camera, scene, renderer;
let scene2, renderer2;
const frustumSize = 500;
init();
animate();
function init() {
const aspect = window.innerWidth / window.innerHeight;
camera = new THREE.OrthographicCamera( frustumSize * aspect / - 2, frustumSize * aspect / 2, frustumSize / 2, frustumSize / - 2, 1, 1000 );
camera.position.set( - 200, 200, 200 );
scene = new THREE.Scene();
scene.background = new THREE.Color( 0xf0f0f0 );
scene2 = new THREE.Scene();
// MeshBasicMaterial: 基础网格材质
// wireframeLinewidth: 控制线框宽度，默认值为1
const material = new THREE.MeshBasicMaterial( { color: 0x000000, wireframe: true, wireframeLinewidth: 1, side: THREE.DoubleSide } );
// left
// Euler: 欧拉角
createPlane(
100, 100,
'chocolate',
new THREE.Vector3( - 50, 0, 0 ),
new THREE.Euler( 0, - 90 * THREE.MathUtils.DEG2RAD, 0 )
);
// right
createPlane(
100, 100,
'saddlebrown',
new THREE.Vector3( 0, 0, 50 ),
new THREE.Euler( 0, 0, 0 )
);
// top
// 这段代码创建了一个尺寸为 100x100 的黄绿色平面，位置位于 (0, 50, 0)，并绕 X 轴逆时针旋转 90 度。
createPlane(
100, 100,
'yellowgreen',
new THREE.Vector3( 0, 50, 0 ),
new THREE.Euler( - 90 * THREE.MathUtils.DEG2RAD, 0, 0 )
);
// bottom
createPlane(
300, 300,
'seagreen',
new THREE.Vector3( 0, - 50, 0 ),
new THREE.Euler( - 90 * THREE.MathUtils.DEG2RAD, 0, 0 )
);
//
renderer = new THREE.WebGLRenderer();
renderer.setPixelRatio( window.devicePixelRatio );
renderer.setSize( window.innerWidth, window.innerHeight );
document.body.appendChild( renderer.domElement );
renderer2 = new CSS3DRenderer();
renderer2.setSize( window.innerWidth, window.innerHeight );
renderer2.domElement.style.position = 'absolute';
renderer2.domElement.style.top = 0;
document.body.appendChild( renderer2.domElement );
const controls = new OrbitControls( camera, renderer2.domElement );
controls.minZoom = 0.5;
controls.maxZoom = 2;
function createPlane( width, height, cssColor, pos, rot ) {
const element = document.createElement( 'div' );
element.style.width = width + 'px';
element.style.height = height + 'px';
element.style.opacity = 0.75;
element.style.background = cssColor;
const object = new CSS3DObject( element );
object.position.copy( pos );
object.rotation.copy( rot );
scene2.add( object );
// PlaneGeometry: 平面缓冲集合体
const geometry = new THREE.PlaneGeometry( width, height );
const mesh = new THREE.Mesh( geometry, material );
mesh.position.copy( object.position );
mesh.rotation.copy( object.rotation );
scene.add( mesh );
}
window.addEventListener( 'resize', onWindowResize );
createPanel();
}
function onWindowResize() {
const aspect = window.innerWidth / window.innerHeight;
camera.left = - frustumSize * aspect / 2;
camera.right = frustumSize * aspect / 2;
camera.top = frustumSize / 2;
camera.bottom = - frustumSize / 2;
camera.updateProjectionMatrix();
renderer.setSize( window.innerWidth, window.innerHeight );
renderer2.setSize( window.innerWidth, window.innerHeight );
}
function animate() {
requestAnimationFrame( animate );
renderer.render( scene, camera );
renderer2.render( scene2, camera );
}
function createPanel() {
const panel = new GUI();
const folder1 = panel.addFolder( 'camera setViewOffset' ).close();
const settings = {
'setViewOffset'() {
folder1.children[ 1 ].enable().setValue( window.innerWidth );
folder1.children[ 2 ].enable().setValue( window.innerHeight );
folder1.children[ 3 ].enable().setValue( 0 );
folder1.children[ 4 ].enable().setValue( 0 );
folder1.children[ 5 ].enable().setValue( window.innerWidth );
folder1.children[ 6 ].enable().setValue( window.innerHeight );
},
'fullWidth': 0,
'fullHeight': 0,
'offsetX': 0,
'offsetY': 0,
'width': 0,
'height': 0,
'clearViewOffset'() {
folder1.children[ 1 ].setValue( 0 ).disable();
folder1.children[ 2 ].setValue( 0 ).disable();
folder1.children[ 3 ].setValue( 0 ).disable();
folder1.children[ 4 ].setValue( 0 ).disable();
folder1.children[ 5 ].setValue( 0 ).disable();
folder1.children[ 6 ].setValue( 0 ).disable();
camera.clearViewOffset();
}
};
folder1.add( settings, 'setViewOffset' );
folder1.add( settings, 'fullWidth', window.screen.width / 4, window.screen.width * 2, 1 ).onChange( ( val ) => updateCameraViewOffset( { fullWidth: val } ) ).disable();
folder1.add( settings, 'fullHeight', window.screen.height / 4, window.screen.height * 2, 1 ).onChange( ( val ) => updateCameraViewOffset( { fullHeight: val } ) ).disable();
folder1.add( settings, 'offsetX', 0, 256, 1 ).onChange( ( val ) => updateCameraViewOffset( { x: val } ) ).disable();
folder1.add( settings, 'offsetY', 0, 256, 1 ).onChange( ( val ) => updateCameraViewOffset( { y: val } ) ).disable();
folder1.add( settings, 'width', window.screen.width / 4, window.screen.width * 2, 1 ).onChange( ( val ) => updateCameraViewOffset( { width: val } ) ).disable();
folder1.add( settings, 'height', window.screen.height / 4, window.screen.height * 2, 1 ).onChange( ( val ) => updateCameraViewOffset( { height: val } ) ).disable();
folder1.add( settings, 'clearViewOffset' );
}
function updateCameraViewOffset( { fullWidth, fullHeight, x, y, width, height } ) {
if ( ! camera.view ) {
camera.setViewOffset( fullWidth || window.innerWidth, fullHeight || window.innerHeight, x || 0, y || 0, width || window.innerWidth, height || window.innerHeight );
} else {
camera.setViewOffset( fullWidth || camera.view.fullWidth, fullHeight || camera.view.fullHeight, x || camera.view.offsetX, y || camera.view.offsetY, width || camera.view.width, height || camera.view.height );
}
}
</script>
</body>
</html>