Three.js Example 注解 —— CombinedCamera.js
作者：互联网
本文搬自我的Github，https://github.com/555chy/three.js-example-comment，有兴趣的可以一起来完善，这个为Three.js的Example进行注解，方便初学者阅读
three.js 官网 Example 地址：https://threejs.org/examples/
/**
* @author zz85 / http://twitter.com/blurspline / http://www.lab4games.net/zz85/blog
*
* A general perpose camera, for setting FOV, Lens Focal Length,
* and switching between perspective and orthographic views easily.
* Use this only if you do not wish to manage
* both a Orthographic and Perspective Camera
*
* 一个通用的相机，设置视场(Forward Observer Vehicle)，透镜焦距，
* 并且可以在透视和正交视图中很容易的切换。
* 只要你不愿意手动管理正交和透视相机，你就可以使用它
*/
//之所以要传递不同的near和far是因为: 透视相机的near必须在相机位置前，而正交相机的near也可以在相机之后
THREE.CombinedCamera = function ( width, height, fov, near, far, orthoNear, orthoFar ) {
/*
call: 调用一个对象的一个方法，以另一个对象替换当前对象
A.call(B)，简单的说就是"B继承了A的所有变量与方法"
*/
THREE.Camera.call( this );
this.fov = fov;
this.left = - width / 2;
this.right = width / 2;
this.top = height / 2;
this.bottom = - height / 2;
// We could also handle the projectionMatrix internally, but just wanted to test nested camera objects
// 你也可以在内部修改该投影矩阵，但只是想测试嵌入相机对象。
this.cameraO = new THREE.OrthographicCamera( width / - 2, width / 2, height / 2, height / - 2, orthoNear, orthoFar );
this.cameraP = new THREE.PerspectiveCamera( fov, width / height, near, far );
this.zoom = 1;
this.toPerspective();
};
/*
var a = new Object(); // 创建一个对象，没有父类
var b = Object.create(a.prototype); // b继承了a的原型
*/
THREE.CombinedCamera.prototype = Object.create( THREE.Camera.prototype );
//下面这句注释掉也不会影响
//THREE.CombinedCamera.prototype.constructor = THREE.CombinedCamera;
THREE.CombinedCamera.prototype.toPerspective = function () {
// Switches to the Perspective Camera
// 切换为透视相机
this.near = this.cameraP.near;
this.far = this.cameraP.far;
this.cameraP.fov = this.fov / this.zoom ;
//更新透视相机投影矩阵
this.cameraP.updateProjectionMatrix();
this.projectionMatrix = this.cameraP.projectionMatrix;
this.inPerspectiveMode = true;
this.inOrthographicMode = false;
};
THREE.CombinedCamera.prototype.toOrthographic = function () {
// Switches to the Orthographic camera estimating viewport from Perspective
// 切换为正交相机，从投影中估算视口
var fov = this.fov;
var aspect = this.cameraP.aspect;
var near = this.cameraP.near;
var far = this.cameraP.far;
// The size that we set is the mid plane of the viewing frustum
// 我们设置的大小是视图锥截体的中心平面
var hyperfocus = ( near + far ) / 2;
var halfHeight = Math.tan( fov * Math.PI / 180 / 2 ) * hyperfocus;
var halfWidth = halfHeight * aspect;
halfHeight /= this.zoom;
halfWidth /= this.zoom;
this.cameraO.left = - halfWidth;
this.cameraO.right = halfWidth;
this.cameraO.top = halfHeight;
this.cameraO.bottom = - halfHeight;
// this.cameraO.left = -farHalfWidth;
// this.cameraO.right = farHalfWidth;
// this.cameraO.top = farHalfHeight;
// this.cameraO.bottom = -farHalfHeight;
// this.cameraO.left = this.left / this.zoom;
// this.cameraO.right = this.right / this.zoom;
// this.cameraO.top = this.top / this.zoom;
// this.cameraO.bottom = this.bottom / this.zoom;
this.cameraO.updateProjectionMatrix();
this.near = this.cameraO.near;
this.far = this.cameraO.far;
this.projectionMatrix = this.cameraO.projectionMatrix;
this.inPerspectiveMode = false;
this.inOrthographicMode = true;
};
THREE.CombinedCamera.prototype.setSize = function( width, height ) {
this.cameraP.aspect = width / height;
this.left = - width / 2;
this.right = width / 2;
this.top = height / 2;
this.bottom = - height / 2;
};
//视场(Field of View)
THREE.CombinedCamera.prototype.setFov = function( fov ) {
this.fov = fov;
if ( this.inPerspectiveMode ) {
this.toPerspective();
} else {
this.toOrthographic();
}
};
// For maintaining similar API with PerspectiveCamera
// 保持与透视相机相似的API
THREE.CombinedCamera.prototype.updateProjectionMatrix = function() {
if ( this.inPerspectiveMode ) {
this.toPerspective();
} else {
//由于正交相机的参数均是由透视相机换算过来的，因此这里要先转为透视相机进行计算
this.toPerspective();
this.toOrthographic();
}
};
/*
* Uses Focal Length (in mm) to estimate and set FOV
* 35mm (full frame) camera is used if frame size is not specified;
* Formula based on http://www.bobatkins.com/photography/technical/field_of_view.html
*
* 使用焦距(以毫米为单位)来估算和设置视场(Field of View)
* 如果帧大小没有被指定，默认会采用35毫米(完整帧)的相机;
* 公式基于 http://www.bobatkins.com/photography/technical/field_of_view.html
*/
THREE.CombinedCamera.prototype.setLens = function ( focalLength, filmGauge ) {
//filmGauge: 薄膜尺寸
if ( filmGauge === undefined ) filmGauge = 35;
//Extent(程度)Slope(斜面)
var vExtentSlope = 0.5 * filmGauge / ( focalLength * Math.max( this.cameraP.aspect, 1 ) );
//THREE.Math.RAD2DEG: 从弧度转换为角度
var fov = THREE.Math.RAD2DEG * 2 * Math.atan( vExtentSlope );
this.setFov( fov );
return fov;
};
THREE.CombinedCamera.prototype.setZoom = function( zoom ) {
this.zoom = zoom;
if ( this.inPerspectiveMode ) {
this.toPerspective();
} else {
this.toOrthographic();
}
};
THREE.CombinedCamera.prototype.toFrontView = function() {
this.rotation.x = 0;
this.rotation.y = 0;
this.rotation.z = 0;
// should we be modifing the matrix instead?
};
THREE.CombinedCamera.prototype.toBackView = function() {
this.rotation.x = 0;
this.rotation.y = Math.PI;
this.rotation.z = 0;
};
THREE.CombinedCamera.prototype.toLeftView = function() {
this.rotation.x = 0;
this.rotation.y = - Math.PI / 2;
this.rotation.z = 0;
};
THREE.CombinedCamera.prototype.toRightView = function() {
this.rotation.x = 0;
this.rotation.y = Math.PI / 2;
this.rotation.z = 0;
};
THREE.CombinedCamera.prototype.toTopView = function() {
this.rotation.x = - Math.PI / 2;
this.rotation.y = 0;
this.rotation.z = 0;
};
THREE.CombinedCamera.prototype.toBottomView = function() {
this.rotation.x = Math.PI / 2;
this.rotation.y = 0;
this.rotation.z = 0;
};
标签：fov,prototype,THREE,Three,CombinedCamera,cameraO,rotation,js 来源： https://blog.csdn.net/chy555chy/article/details/104861589