[vtkusers] Update on VTK 6

[Berk Geveci]

Hi folks,

I just wanted to send a quick note about our progress towards a VTK 6
release. We have been working very hard on some new features and
cleaning up some difficult to maintain legacy code in VTK. Therefore,
there are some significant changes in VTK 6 some of which are not
backwards compatible. Some of these are summarized in here:

http://www.vtk.org/Wiki/VTK#VTK_6.0_.28pending.29

Of particular importance are these two links:

http://www.vtk.org/Wiki/VTK/VTK_6_Migration_Guide
http://www.vtk.org/Wiki/VTK/Build_System_Migration

If you see missing information on these pages, please help us out by
sending a quick not or even better adding them directly to the Wiki.

We have also been working hard at cleaning the VTK dashboards and have
made great progress. Kudos to the whole team for the hard work over
the last few weeks and specially to Bill Lorensen for leading the
charge.

As for the release date, we don't have a firm one yet. We are shooting
for mid to late April for now. We'll send updates as things firm up.
This is a good time to start testing your code with VTK 6 if you plan
on moving forward.

Finally, we expect that there will continue to be some larger changes
that may impact API coming after VTK 6. We are looking at things like:

- Thread safety and better support for shared memory parallelism
- Improved data model (i.e. improvement to vtkDataObject and sub-classes)
- Major refactoring of rendering modules (hopefully)

So VTK 7 should not be very far in the horizon. Maybe in another year.

Best,
-berk