[vtkusers] vtkResliceImageViewer hides cross hairs in certain positions

[Jean-Hugues Royer]

Hi,

This is a late reply but I think you might run in the recently problem 
of deprecated OpenGL list.

Basically when you are using a vtkPolyDataMapper, which is probably what 
your crosshair widget is using, you need to set 
ImmediateModeRenderingOn() to avoid hidden/black rendering.

The problem is explained in this vtk developpers post:

http://www.vtk.org/pipermail/vtk-developers/2012-June/011832.html

I'm not using vtkResliceImageViewer, but the one I coded had the same 
issue until I enabled immediate mode rendering.

It would be a good idea to try to set it manually if you access the 
crosshair mapper or by patching the source of the widget...

Regards.