Actionscript 3.0, good OOP?

I have been coding for some time (3 years I think), and have recently been wondering if my coding pattern is any good. Any kind of feedback is welcome:

EDIT: The thing that concerns me most is that I have read a lot around that getters/setters are bad for OOP. Is this true?

//Point3D.as
public class Point3D 
{
    private var _x:int;
    private var _y:int;
    private var _z:int;

    public function Point3D(tx:int = 0, ty:int = 0, tz:int = 0)
    {
        _x = tx;
        _y = ty;
        _z = tz;
    }

    public function get x():int { return _x; }
    public function set x(tv:int):void { _x = tv; }

    public function get y():int { return _y; }
    public function set y(tv:int):void { _y = tv; }

    public function get z():int { return _z; }
    public function set z(tv:int):void { _z = tv; }

}

//Geometry3D.as
public class Geometry3D
{
    private var _indices:Vector.<uint>;
    private var _vertices:Vector.<Number>;

    public function Geometry3D(tindices:Vector.<uint>,
    tvertices:Vector.<Number>)
    {
        _indices = tindices;
        _vertices = tvertices;
    }

    public function get indices():Vector.<uint> { return _indices; }
    public function get vertices():Vector.<Number> { return _vertices; }

}

//Primitive3D.as
public class Primitive3D 
{
    private var _position:Point3D;
    private var _geometry:Geometry3D;

    public function Primitive3D(tx:int, ty:int, tz:int, tgeometry:Geometry3D) 
    {
        _position = new Point3D(tx, ty, tz);
        _geometry = tgeometry;
    }

    public function get position():Point3D { return _position; }
    public function get geometry():Geometry3D { return _geometry; }

    public function render():void
    {
        //add render code here
    }

}

//TrianglePrimitive.as
public class TrianglePrimitive extends Primitive3D
{

    public function TrianglePrimitive(tx:int, ty:int, tz:int)
    {
        var indices:Vector.<uint> = Vector.<uint>([
        0, 1, 2]);
        var vertices:Vector.<Number> = Vector.<Number>([
        ]);

        var geo:Geometry3D = new Geometry3D(indices, vertices);
        super(tx, ty, tz, geo);
    }

    public function spin(tradians:Number):void
    {
        //add spin code here
    }

}

//Main.as
...
var tri:TrianglePrimitive = new TrianglePrimitive(0, 0, 0);
tri.position.z = -4;
tri.spin(Math.PI / 2); //90 degrees
tri.render(); 
...

Again, thanks a bunch for any feedback!