[vtk-developers] Volume rendering very large StructuredGrids

[David Gobbi]

Yes, both the mapper and the space-leaper filter had 32-bit overflow bugs.
These bugs were reported a couple months ago, and the fix was merged
a few days ago, just before the VTK tree was modularized.

To update your tree to the merge commit, which will bring in all the
VTK 6 pipeline changes but none of the modularization changes, do
the following:

git fetch origin master
git merge fc4c570a

To avoid all the VTK 6 pipeline changes, you can try cherry-picking
the fix (it's commit a3feef0d) but no guarantees.

If you get a chance to test the fix, please report your findings.  The
more testing that this code gets, the better.

 - David


On Tue, Apr 10, 2012 at 8:03 PM, Jim Geach <jimgeach at physics.mcgill.ca> wrote:
>
> Dear developers,
>
> I am using vtkFixedPointVolumeRayCastMapper to render very large (1536^3) volumes with two data components. So far, I have been unsuccessful in properly rendering volumes when the number of elements >MAX_INT. I'm using v5.11.0.
>
> Independent checks (e.g. simple 2D projections of the data) show that the problem is not with the data, but in the rendering itself.
>
> I have built VTK with USE_64BIT indexing ON, and the volume rending actually completes and dumps an image without complaint. However, but the image is garbled: it looks broadly correct, but some chunks are missing, there are large discontinuities, etc.
>
> Is this a bug? e.g. is there some int casting within a function of vtkFixedPointVolumeRayCastMapper (space leaping?) or associated volume rendering code that prevents VTK from properly volume rendering of 64-bit class data arrays?
>
> Any help on this issue would be very gratefully received!
>
> Thanks, Jim