Flash/Flex学习笔记(51)：3维旋转与透视变换(PerspectiveProjection)

Flash/Flex学习笔记(49)：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

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

得到一个图片的Bigmap实例