三角形类

来源：互联网发布：初识动画软件教学设计编辑：程序博客网时间：2024/04/26 06:07

// Triangle Class

package {
   import flash.display.Graphics;
   public class Triangle {
       private var pointA:Point3D;
       private var pointB:Point3D;
       private var pointC:Point3D;
       private var color:uint;
       public function Triangle(a:Point3D, b:Point3D, c:Point3D, color:uint) {
           pointA = a;
           pointB = b;
           pointC = c;
           this.color = color;
       }
       public function draw(g:Graphics):void {
           if (isBackFace())
           {
               return;
           }
            g.beginFill(color);
           g.moveTo(pointA.screenX, pointA.screenY);
           g.lineTo(pointB.screenX, pointB.screenY);
           g.lineTo(pointC.screenX, pointC.screenY);
           g.lineTo(pointA.screenX, pointA.screenY);
           g.endFill();
       }

       private function isBackFace():Boolean {
           // 见 http://www.jurjans.lv/flash/shape.html
           var cax:Number = pointC.screenX - pointA.screenX;
           var cay:Number = pointC.screenY - pointA.screenY;
           var bcx:Number = pointB.screenX - pointC.screenX;
           var bcy:Number = pointB.screenY - pointC.screenY;
           return cax * bcy > cay * bcx;
       }
        public function get depth():Number {
           var zpos:Number = Math.min(pointA.z, pointB.z);
           zpos = Math.min(zpos, pointC.z);
           return zpos;
    }

   }
}