[ActionScript 3.0] 透视投影

下面的示例演示如何使用透视投影来创建 3D 空间。该示例演示如何通过projectionCenter属性来修改消失点和更改空间的透视投影。进行这种修改后，将强制重新计算focalLength和fieldOfView（及其相关的 3D 空间扭曲）。

此示例：

1. 创建一个名为center的 sprite，作为包含十字准线的圆

2. 将centersprite 的坐标指定给根的transform属性的perspectiveProjection属性的projectionCenter属性

3. 为鼠标事件添加事件侦听器，用于调用修改projectionCenter的处理程序，以便跟踪center对象的位置

4. 创建四个折叠样式的框，这四个框将形成透视空间的墙壁

在测试此示例时，ProjectionDragger.swf 将圆拖动到不同的位置。消失点将跟随圆移动，直到释放圆时才固定下来。在移动投影中心使其远离舞台中心时，观察包围空间的框所发生的拉伸和出现的扭曲。

 package
 {
     import flash.display.Sprite;
     import flash.display.Shape;
     import flash.geom.Point;
     import flash.events.*;
     public class ProjectionDragger extends Sprite
     {
         private var center:Sprite;
         private var boxPanel:Shape;
         private var inDrag:Boolean = false;

         public function ProjectionDragger():void
         {
             createBoxes();
             createCenter();
         }
         public function createCenter():void
         {
             var centerRadius:int = 20;

             center = new Sprite  ;

             // circle
             center.graphics.lineStyle(1,0x000099);
             center.graphics.beginFill(0xCCCCCC,0.5);
             center.graphics.drawCircle(0,0,centerRadius);
             center.graphics.endFill();
             // cross hairs ;
             center.graphics.moveTo(0,centerRadius);
             center.graphics.lineTo(0, -  centerRadius);
             center.graphics.moveTo(centerRadius,0);
             center.graphics.lineTo( -  centerRadius,0);
             center.x = 175;
             center.y = 175;
             center.z = 0;
             this.addChild(center);

             center.addEventListener(MouseEvent.MOUSE_DOWN,startDragProjectionCenter);
             center.addEventListener(MouseEvent.MOUSE_UP,stopDragProjectionCenter);
             center.addEventListener(MouseEvent.MOUSE_MOVE,doDragProjectionCenter);
             root.transform.perspectiveProjection.projectionCenter = new Point(center.x,center.y);
         }
         public function createBoxes():void
         {
             // createBoxPanel();
             var boxWidth:int = 50;
             var boxHeight:int = 50;
             var numLayers:int = 12;
             var depthPerLayer:int = 50;

             // var boxVec:Vector.<Shape> = new Vector.<Shape>(numLayers);
             for (var i:int = 0; i < numLayers; i++) {
                 this.addChild(createBox(150,50,(numLayers - i) * depthPerLayer,boxWidth,boxHeight,0xCCCCFF));
                 this.addChild(createBox(50,150,(numLayers - i) * depthPerLayer,boxWidth,boxHeight,0xFFCCCC));
                 this.addChild(createBox(250,150,(numLayers - i) * depthPerLayer,boxWidth,boxHeight,0xCCFFCC));
                 this.addChild(createBox(150,250,(numLayers - i) * depthPerLayer,boxWidth,boxHeight,0xDDDDDD));
             }
         }

         public function createBox(xPos:int=0,yPos:int=0,zPos:int=100,w:int=50,h:int=50,color:int=0xDDDDDD):Shape
         {
             var box:Shape = new Shape  ;
             box.graphics.lineStyle(2,0x666666);
             box.graphics.beginFill(color,1.0);
             box.graphics.drawRect(0,0,w,h);
             box.graphics.endFill();
             box.x = xPos;
             box.y = yPos;
             box.z = zPos;
             return box;
         }
         public function startDragProjectionCenter(e:Event)
         {
             center.startDrag();
             inDrag = true;
         }

         public function doDragProjectionCenter(e:Event)
         {
             if (inDrag) {
                 root.transform.perspectiveProjection.projectionCenter = new Point(center.x,center.y);
             }
         }

         public function stopDragProjectionCenter(e:Event)
         {
             center.stopDrag();
             root.transform.perspectiveProjection.projectionCenter = new Point(center.x,center.y);
             inDrag = false;
         }
     }
 }

效果如图：