In class mitkPointSetVtkMapper3D, there are code fragments about whether an input device is connected (PositionTracker) to MITK. This is evaluated in the property "inputdevice". If a PositionTracker is connected, the resolution of the spheres which are rendered is decreased.
This is a solution for a very individual problem, so it should be removed from the code. A more generic solution would be to offer an overall property where the user can set the resolution of the spheres (= number of vertices per sphere) indenpend of any input device.