[vtkusers] Render order - Depth sorting volumes

[Simon Adler]

Dear Members,

how can i change the order in which volumes are rendered. Or more in
general - how can i change the order objects are rendered (not cells
within objects).

Concrete Problem:
I have to Volumerenderings close to each other but not overlapping. I
do not want to use Depth peeling, due to performance reasons. I just
want to change the order how the are rendered depening on the current
camera position.

I tried...
... to sort the vtkVolumeCollection got from the renderer, but this
has no effect.

My renderer is a vtkOpenGLRenderer. Volumes are represented by
vtkSmartVolumeMapper.

Thanks for any advice

Simon Adler