Bounding ellipse of sphere in 2D - what's wrong?

Bounding ellipse of sphere in 2D - what's wrong?
@author makc

forked:1
favorite:2
lines:61
license : see code comments
modified : 2009-06-14 22:46:50

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package  
{
	import caurina.transitions.Tweener;
	import flash.display.Sprite;
	import flash.events.Event;
	import sandy.core.Scene3D;
	import sandy.core.scenegraph.Camera3D;
	import sandy.core.scenegraph.Group;
	import sandy.core.scenegraph.Shape3D;
	import sandy.primitive.GeodesicSphere;
	import sandy.primitive.Sphere;

[SWF(width=465, height=465, frameRate=30, backgroundColor=0xFFFFFF)]

/**
	* Bounding ellipse of sphere in 2D - what's wrong?
	* @author makc
	*/
	public class CircleTest extends Sprite {
		private var container:Sprite;
		private var scene:Scene3D;
		private var sphere:Shape3D;
		private var R:Number = 100;

public function CircleTest () {
			container = Sprite (addChild (new Sprite));
			scene = new Scene3D ("scene", container, new Camera3D (2000, 465), new Group ("root"));
			sphere = new GeodesicSphere ("sphere", R, 3); // new Sphere ("sphere", R);
			sphere.z = 400; scene.root.addChild (sphere);
			toLeft ();

addEventListener (Event.ENTER_FRAME, onEnterFrame);
		}

private function toLeft ():void {
			Tweener.addTween (sphere, { x: -1500, time: 4, transition:"linear", onComplete:toRight });
		}

private function toRight ():void {
			Tweener.addTween (sphere, { x: +1500, time: 4, transition:"linear", onComplete:toLeft });
		}

private function onEnterFrame (e:Event):void {
			// sphere camera coords
			var sz:Number = (sphere.z - scene.camera.z);
			var sx:Number = sphere.x;

// screen coords
			var sx_screen:Number = sx * scene.camera.focalLength / sz;
			var R_screen:Number = R * scene.camera.focalLength / sz;

// distance to sphere
			var sd:Number = Math.sqrt (sx*sx + sz*sz);

// angles
			var a:Number = Math.asin (R / sd);
			var b:Number = Math.asin (sx / sd);

// apsides
			var dm:Number = R_screen / Math.cos (b - a);
			var dp:Number = R_screen / Math.cos (b + a);

// semiaxes
			var A:Number = 0.5 * (dm + dp);
			var B:Number = sd * Math.tan (a) * scene.camera.focalLength / sz;

// show stuff
			scene.render ();
			x = 462/2 -1000 -sx_screen;
			container.graphics.clear ();
			container.graphics.beginFill (0xFF00);
			container.graphics.drawRect (1000 +sx_screen -4, 465/2 -4, 8, 8);
			container.graphics.endFill ();
			container.graphics.lineStyle (1, 0xFF0000);
			container.graphics.moveTo (1000 +sx_screen -dm, 465/2 -40);
			container.graphics.lineTo (1000 +sx_screen -dm, 465/2 +40);
			container.graphics.moveTo (1000 +sx_screen +dp, 465/2 -40);
			container.graphics.lineTo (1000 +sx_screen +dp, 465/2 +40);
			container.graphics.drawEllipse (1000 +sx_screen -dm, 465/2 - B, 2*A, 2*B);

// randomize
			sphere.rotateX += Math.random ();
			sphere.rotateY += Math.random ();
			sphere.rotateZ += Math.random ();
		}
		
	}
	
}

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