[away3d] Ess Guide to Away3D - ch.4 - Segments

[rowild]

Hi,

I bought the book "The Essential Guide to 3D in Flash", which is
totally about Away3D. I am in chapter 4, where this code is posted
(compared to the book, I changed the names of the classes):

// Base Class
package
{
        import away3d.core.base.*;
        import away3d.cameras.*;
        import away3d.containers.*;

        import flash.display.*;
        import flash.events.*;

        public class Away3D_BaseClass2 extends Sprite
        {
                protected var _camera:HoverCamera3D;
                protected var _view:View3D;

                public function Away3D_BaseClass2()
                {
                        super();
                        _createView();
                        _createScene();
                }

                protected function _createView():void
                {
                        _camera = new HoverCamera3D();
                        _camera.distance = 1000;
                        _camera.tiltAngle = 10;
                        _camera.panAngle = 180;

                        _view = new View3D();
                        _view.x = 400;
                        _view.y = 300;
                        _view.camera = _camera;

                        addChild(_view);
                        addEventListener(Event.ENTER_FRAME, _onEnterFrame);
                }

                protected function _createScene():void
                {
                        // To be overridden
                }

                protected function _onEnterFrame(ev : Event):void
                {
                        _camera.panAngle += (stage.mouseX - stage.stageWidth/2) 
/ 100;
                        _camera.hover();
                        //_camera.steps = 2;

                        _view.render();
                }
        }
}


// Extending Class (in new File of course)
package
{
        import away3d.core.math.*;
        import away3d.primitives.LineSegment;

        [SWF(width="800",height="600")]

        public class Away3D_drawLines extends Away3D_BaseClass2
        {
                public function Away3D_drawLines():void
                {
                        super();
                }

                override protected function _createScene():void
                {
                        var i:int, p1:Number3D, p2:Number3D, seg:LineSegment;

                        p1 = new Number3D();
                        p2 = new Number3D();

                        for (i=0; i < 5; i++)
                        {
                                p2.x = (Math.random() - 0.5) *200;
                                p2.y = (Math.random() - 0.5) *200;
                                p2.z = (Math.random() - 0.5) *200;

                                p2.add(p2, p1);

                                seg = new LineSegment();
                                seg.start = p1;
                                seg.end = p2;

                                _view.scene.addChild(seg);

                                p1.clone(p2);
                        }
                }
        }
}

and this error message shows up in my Flash CS5:
/...h/Away3D_drawLines.as, Line 31      1067: Implicit coercion of a value
of type away3d.core.math:Number3D to an unrelated type
away3d.core.base:Vertex.

I cannot solve this problem, and there is no Errata page at friendsof
ed.com.

Can anybody give me a hint what's wrong here?
Thanks!