Flash/Flex学习笔记(45)：3维旋转与透视变换(PerspectiveProjection)

Flash/Flex学习笔记：3D基础 里已经介绍了3D透视的基本原理，不过如果每次都要利用象该文中那样写一堆代码，估计很多人不喜欢，事实上AS3的DisplayObject类已经内置了z坐标、rotationX、rotationY、rotationZ属性，再加上PerspectiveProjection类用于处理透视转换，基本上可以满足大多数的3D要求。

 
import flash.events.Event;

 
import flash.display.Sprite;

 
import flash.text.TextField;

 
import flash.events.MouseEvent;

import flash.text.TextFieldAutoSize;

var isAngleChangeing = false;

 
var txtX:TextField,txtY:TextField,txtZ:TextField,txtPosZ:TextField,txtFieldOfView:TextField,txtInfo:TextField,txtCenter:TextField,txtFocusLength:TextField;

 
txtX = new TextField();

 
txtX.text = "rotationX：";

 
txtY = new TextField();

 
txtY.text = "rotationY：";

 
txtZ = new TextField();

 
txtZ.text = "rotationZ：";

 
txtPosZ = new TextField();

 
txtPosZ.text = "Z：";

 
txtFieldOfView = new TextField();

 
txtFieldOfView.text = "视角：";

 
txtCenter = new TextField();

 
txtCenter.text = "消失点："

 
txtFocusLength = new TextField();

 
txtFocusLength.text = "焦距：";

 
txtX.y = txtY.y = txtZ.y = 5;

 
txtX.x = txtPosZ.x = 10;

 
txtPosZ.y = txtX.y + 26;

 
txtPosZ.x +=  40;

 
txtY.x = txtX.x + 180;

 
txtZ.x = txtY.x + 180;

 
txtFieldOfView.x = txtPosZ.x + 160;

 
txtFieldOfView.y = txtPosZ.y;

 
txtCenter.x = txtFieldOfView.x + 170;

 
txtCenter.y = txtPosZ.y;

 
txtInfo = new TextField();

 
txtInfo.text="";

 
txtFocusLength.x = txtX.x + 25;

txtFocusLength.y = txtPosZ.y + 25;

var imgBD:BitmapData = new ImgSample();

 
var img:Bitmap = new Bitmap(imgBD);

 
trace("img.width=",img.width,"，img.height=",img.height);

var imgSprite:Sprite = new Sprite();

 
img.x =  -  img.width / 2;

img.y =  -  img.height / 2;

 
imgSprite.addChild(img);

 
trace("imgSprite.width=",imgSprite.width,"，imgSprite.height=",imgSprite.height);

 
var containerSprite:Sprite = new Sprite();

 
containerSprite.addChild(imgSprite);

 
imgSprite.x = img.width / 2;

imgSprite.y = img.height / 2;

addChild(containerSprite);

trace("containerSprite.width=",containerSprite.width,"，containerSprite.height=",containerSprite.height);

 
containerSprite.x = stage.stageWidth / 2 - containerSprite.width / 2;

 
containerSprite.y = stage.stageHeight / 2 - containerSprite.height / 2;

containerSprite.z = 50;

 
var silderX:SimpleSlider = new SimpleSlider(0,360,0);

 
silderX.x = txtX.x + 160;

 
silderX.y = txtX.y + 7;

silderX.rotation = 90;

 
var silderY:SimpleSlider = new SimpleSlider(0,360,0);

 
silderY.x = txtY.x + 160;

 
silderY.y = silderX.y;

 
silderY.rotation = 90;

 
var silderZ:SimpleSlider = new SimpleSlider(0,360,0);

 
silderZ.x = txtZ.x + 160;

 
silderZ.y = silderX.y;

 
silderZ.rotation = 90;

 
var silderPosZ:SimpleSlider = new SimpleSlider(-200,200,50);

 
silderPosZ.x = txtX.x + 160;

 
silderPosZ.y = silderX.y + 25;

 
silderPosZ.rotation = 90;

 
var silderFieldOfView:SimpleSlider = new SimpleSlider(0.1,179.9,90);

 
silderFieldOfView.x = silderPosZ.x + 180;

 
silderFieldOfView.y = silderPosZ.y;

silderFieldOfView.rotation = 90;

 
var silderCenterPos:SimpleSlider = new SimpleSlider(150,400,275);

 
silderCenterPos.x = silderFieldOfView.x + 180;

 
silderCenterPos.y = silderPosZ.y;

 
silderCenterPos.rotation = 90;

 
var silderFocusLength:SimpleSlider = new SimpleSlider(100,500,300);

 
silderFocusLength.x = silderPosZ.x ;

 
silderFocusLength.y = silderPosZ.y + 25;

 
silderFocusLength.rotation = 90;

 
addChild(txtX);

 
addChild(txtY);

 
addChild(txtZ);

 
addChild(txtPosZ);

 
addChild(txtFieldOfView);

 
addChild(txtInfo);

 
addChild(txtCenter);

 
addChild(txtFocusLength);

 
addChild(silderX);

 
addChild(silderY);

 
addChild(silderZ);

 
addChild(silderPosZ);

 
addChild(silderFieldOfView);

 
addChild(silderCenterPos);

 
addChild(silderFocusLength);

 
silderX.addEventListener(Event.CHANGE,silderXChangeHandler);

 
silderY.addEventListener(Event.CHANGE,silderYChangeHandler);

 
silderZ.addEventListener(Event.CHANGE,silderZChangeHandler);

 
silderPosZ.addEventListener(Event.CHANGE,silderPosZChangeHandler);

 
silderFieldOfView.addEventListener(Event.CHANGE,silderFieldOfViewChangeHandler);

silderFieldOfView.addEventListener(MouseEvent.MOUSE_UP,function(){isAngleChangeing = false});

 
silderCenterPos.addEventListener(Event.CHANGE,silderCenterPosChangeHandler);

 
silderFocusLength.addEventListener(Event.CHANGE,silderFocusLengthChangeHandler);

 
function showTxtInfo(s:SimpleSlider){

txtInfo.text = s.value.toString().substr(0,5);

 
txtInfo.x = mouseX + 20;

 
txtInfo.y = s.y + 5;

 
}

function silderXChangeHandler(e:Event):void {

 
imgSprite.rotationX = silderX.value;

 
showTxtInfo(silderX);

 
}

 
function silderYChangeHandler(e:Event):void {

imgSprite.rotationY = silderY.value;

showTxtInfo(silderY);

 
}

 
function silderZChangeHandler(e:Event):void {

 
imgSprite.rotationZ = silderZ.value;

 
showTxtInfo(silderZ);

 
}

 
function silderPosZChangeHandler(e:Event):void {

 
containerSprite.z = silderPosZ.value;

 
showTxtInfo(silderPosZ);

 
}

function silderFieldOfViewChangeHandler(e:Event):void {

 
doPerspectiveProjection();

 
showTxtInfo(silderFieldOfView);

 
isAngleChangeing = true;

 
}

 

function silderCenterPosChangeHandler(e:Event):void {

 
doPerspectiveProjection();

 
showTxtInfo(silderCenterPos);

 
}

 
function silderFocusLengthChangeHandler(e:Event):void {

 
doPerspectiveProjection();

showTxtInfo(silderFocusLength);

 
}

 
function doPerspectiveProjection():void{

 
var pp:PerspectiveProjection=new PerspectiveProjection();

pp.fieldOfView = silderFieldOfView.value;

 
if (!isAngleChangeing){

 
pp.focalLength  = silderFocusLength.value;  

 
}

//trace(pp.focalLength);

 
pp.projectionCenter = new Point(silderCenterPos.value,silderCenterPos.value);

 
containerSprite.transform.perspectiveProjection = pp;

 
}

 
doPerspectiveProjection();

 
var txtAuthor:TextField = new TextField();

 
txtAuthor.htmlText ="<a href='http://yjmyzz.cnblogs.com/' target='_blank'>by 菩提树下的杨过</a>";

 
addChild(txtAuthor);

txtAuthor.y = txtFocusLength.y;

 
txtAuthor.x = 425;

 
txtAuthor.autoSize = TextFieldAutoSize.LEFT;

稍加解释:

z坐标：即对象在z轴上的坐标，flash默认采用的是右手三维坐标，也就是说z值越大，物体越小

rotaionX,rotationY,rotationZ：即对象绕着x,y,z轴旋转的角度

PerspectiveProjection对象的三个属性:

1.focalLength 即焦距，使用效果上貌似焦距越大，物体也越大(?跟常规理解的不同)，而且据官方帮助上讲：在透视转换过程中，将使用视野的角度和舞台的高宽比（舞台宽度除以舞台高度）来自动计算 focalLength

2.fieldOfView 即观察点的三维"视角"(0到180之间的值)，怎么理解我还没想好，不过在使用效果上，如果当物体的z轴坐标不为0时，该值越大，物体的扭曲和形变越夸张，而且动态调整该值时focalLength值也会自动重新计算。(所以如果用代码写死了focalLength，不管如何调整fieldOfView都是看不到效果的)

3.projectionCenter:即3D透视中的消失点，当z轴坐标趋近于无限大时，物体越趋向于该点(消失)。

最后：上面的代码中暗藏了二个小技巧

1.为啥要先把图片放到imgSprite中，然后再将imgSprite又放到containerSprite中?

因为旋转时有一个旋转的中心点，而Flash默认这个中心就是对象的左顶点，即(0,0)位置，用二个sprite嵌套后，再配合坐标的设定，巧妙的将中心点正好移动到了图片中心，如下图：

2.如何用代码从库里取出一张图片?

如上图，关键在于导入图片时要指定“类”名，这样在代码中就可以用

1
var imgBD:BitmapData = new ImgSample();//从库中取出一张图片

2
var img:Bitmap = new Bitmap(imgBD);

得到一个图片的Bigmap实例