[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：