public function getVel(R:Vector.<Number>, t:Vector.<Number>):void
        {
            var data:Vector.<Number> = new Vector.<Number>(16);
            data[0] = R[0];
            data[1] = R[3];
            data[2] = R[6];
            data[3] = 0.0;
            data[4] = R[1];
            data[5] = R[4];
            data[6] = R[7];
            data[7] = 0.0;
            data[8] = R[2];
            data[9] = R[5];
            data[10] = R[8];
            data[11] = 0.0;
            data[12] = t[0];
            data[13] = t[1];
            data[14] = t[2];
            data[15] = 1.0;

            var o:Vector3D = new Vector3D(0, 0, 0);
            var u:Vector3D = new Vector3D(1, 0, 0);
            var v:Vector3D = new Vector3D(0, 1, 0);

            var mat:flash.geom.Matrix3D = new flash.geom.Matrix3D(data);

            var ot:Vector3D = mat.transformVector(o);
            var ut:Vector3D = mat.transformVector(u);
            var vt:Vector3D = mat.transformVector(v);

            _yax_x = ut.y - ot.y;
            _yax_z = vt.y - ot.y;
        }