Three.js之照相机Camera

来源：互联网发布：godaddy 域名续费编辑：程序博客网时间：2024/04/28 19:03

1、背景介绍

在网页显示出三维的效果，就要借助于视觉效果来实现，比如阴影、光照等。这里的Camera相当于人的眼睛，从坐标的那个视点去观察目标，相当于投影出立体感。这里首先说一下坐标。如下图所示：

z轴正方向指向屏幕外，x，y平面在屏幕上。坐标原点（0,0,0）默认为场景中心。照相机就是在这个坐标系中定义的。有两种投影方式：正交投影和透视投影。对于这两种投影具体介绍，请点击这里了解更多。

2、正交投影照相机和透视投影照相机

2.1正交投影照相机

正交投影照相机（Orthographic Camera），构造函数：

OrthographicCamera( left, right, top, bottom, near, far )

left — Camera frustum left plane.
right — Camera frustum right plane.
top — Camera frustum top plane.
bottom — Camera frustum bottom plane.
near — Camera frustum near plane.
far — Camera frustum far plane.

实例演示：

<span style="white-space:pre"></span>//创建场景var scene=new THREE.Scene();//创建相机var camera_Or=new THREE.OrthographicCamera(window.innerWidth/-2,window.innerWidth/2,window.innerHeight/2,window.innerHeight/-2,1,1000);//camera_Or.position.z=5;camera_Or.position.set(50,-20,50);camera_Or.lookAt(new THREE.Vector3(0,0,0))scene.add(camera_Or);drawAxes(scene);//创建渲染器var renderer=new THREE.WebGLRenderer();renderer.setSize(window.innerWidth,window.innerHeight);document.body.appendChild(renderer.domElement);//创建立方体var geometry=new THREE.BoxGeometry(100,100,100);var material=new THREE.MeshBasicMaterial({color:0x00ff00,wireframe:true});var cube=new THREE.Mesh(geometry,material);scene.add(cube);//渲染场景var render=function(){requestAnimationFrame(render);renderer.render(scene,camera_Or);}render();

实例效果图：

2.2透视投影照相机

透视投影照相机（Perspective Camera）的相关构造函数：

PerspectiveCamera( fov, aspect, near, far )

fov — Camera frustum vertical field of view.
aspect — Camera frustum aspect ratio.
near — Camera frustum near plane.
far — Camera frustum far plane.

示例代码：

//创建场景var scene=new THREE.Scene();//创建相机//var camera_Or=new THREE.OrthographicCamera(window.innerWidth/-2,window.innerWidth/2,window.innerHeight/2,window.innerHeight/-2,1,1000);//camera_Or.position.z=5;//camera_Or.position.set(50,-20,50);//camera_Or.lookAt(new THREE.Vector3(0,0,0));var camera_Pe = new THREE.PerspectiveCamera( 75, window.innerWidth/window.innerHeight, 0.1, 1000 );//camera_Pe.position.x=5;//camera_Pe.position.y=5;//camera_Pe.position.z=10;//设置照相机的位置camera_Pe.position.set(3,5,5);//照相机默认是沿着z轴负方向观察的，改为（10,10,10）这个观察点后肯定看到的是一片漆黑//所以，应该指向原点才能看到物体camera_Pe.lookAt(new THREE.Vector3(0,0,0));//camera_Pe.view=(0,0,5);scene.add(camera_Pe);//drawAxes(scene);//创建渲染器var renderer=new THREE.WebGLRenderer();renderer.setSize(window.innerWidth,window.innerHeight);document.body.appendChild(renderer.domElement);//创建立方体var geometry=new THREE.BoxGeometry(1,1,1);var material=new THREE.MeshBasicMaterial({color:0x00ff00,wireframe:true});var cube=new THREE.Mesh(geometry,material);scene.add(cube);//渲染场景var render=function(){requestAnimationFrame(render);renderer.render(scene,camera_Pe);}render();

实例效果图：

3、注意事项

照相机默认的观察方向是指向z轴负方向（就是朝向屏幕），所以当变化坐标以后，就要将照相机指向原点，才能观察到物体。这里调用了lookAt（）函数。用法：camera.lookAt(new THREE.Vector3(0,0,0));这里你可以改成自己的坐标。摄像机观察方向问题一定要调整正确，否则观察不到物体！！！

参考资料：

http://my.oschina.net/u/1455799/blog/213962

http://www.ituring.com.cn/article/48665

0 0