this is a geometry issue, zooming out a lot lets the dataset appear.

it is not really a geometry issue but rather the fact that the vfib files are saved as world coordinates because the fiber bundle stores them in this way. i think the issue will be resolved with the new fiber bundle data structure.

if you load the according image and rest, everything is visualized nicely. but still the issue remains.

You are right, together with the image the visualization works.

What do you think, should we live with this bug for the release and delete the blocking of T9596? Or is there a quick fix you can think of?

I don't think there is quick fix is possible there. But I will ask Iggy. We would need to store the index coordinates in the internal vtkPalyData, because the vtkPalyData writer directly writes everything as it is stored.