public LineSegment3DLW(LineSegment3D l3d)
{
startpoint = new Point3DLW(l3d.startPoint);
endpoint = new Point3DLW(l3d.endPoint);
}
public Rect3DLW(Rect3D rect)
{
min = new Point3DLW(rect.Min);
max = new Point3DLW(rect.Max);
}