[vtkusers] New feature in vtkRIBExporter

[Andy Cedilnik]

Hello!

I added new feature to RIB exporter. Renderman has a nice feature of
passing arbitrary per-vertex arguments to the shader. I used this
feature in several visualization research projects. So far, it was
relatively difficult if not impossible to pass scalar data to the
shader.

This is why I added code in the vtkRIBExporter that exports all
scalars with the rest of the data. This way you can for example
have scalar called "perturbation" and you can use it in the shader
to define the amount of perturbation of the shader at that point.

The only drawback I can see so far is the fact that RIB files are
much bigger. If that will be a problem, I will add a flag to the
vtkRIBExporter to enable or disable this feature.

Hope anybody will use it.

			Andy