Using the Render Window Manager to manipulate the render windows, so that for example the first and the second render window both show their loaded image in the same anatomical plane, the crosshair disappears and only one line is visible.
If all 2D-render windows show their loaded image in the same anatomical plane, the crosshair and the helper planes are not visible anymore.
This is due to the fact that the crosshair is just the point of intersection of the helper planes. Since these helper planes are now parallel instead of orthogonal, they don't have a point of intersection anymore.
I would like to discuss different approaches to solve this problem, like introducing a real crosshair or adding more fixed helper planes.