[Paraview] Problems combining volume and line data

[Richard Beare]

Hello,
I have some image data that I'd like to volume render. It starts out
as a nifti file and I can view it in paraview after conversion to a
vtk structured grid (using the ITK ConvertBetweenFileFormats tool). I
also have some line data (DTI tracts) that I have converted to
ploydata lines. I can view these (but there is a question about that
later). My problem is that the coordinate systems for the two do not
match up. I also have a converter that transforms the image to
polydata, by using the world coordinates for each pixel. This seems to
match up nicely with the DTI tracts, but of course I can't view this
with the volume renderer. The problem seems to be that the x and y
axes in the structured data seem to be wrong (flipped). Any
suggestions on how to convert images for viewing by paraview and
keeping track of world coordinates?

Also, I'd like to be able to colour my lines by orientation. I can't
figure out how to do this. Is it necessary to include local difference
information in the polydata file, or can I get paraview to compute
this for me for each edge?

Thanks