[vtkusers] vtkFixedPointVolumeRayCastMapper question...

[Charles Boivin]

I have recently been working on implementing multiple volume rendering
in our application. Previously, we only had one volume (from one
scalar) showing at any given time, but there is now some need for
rendering of multiple volumes (from multiple, independent, scalars).

I have now just realized that VTK 4.4 cannot handle this -- either
from the texture mappers or from the ray-tracing mappers. Recent
discussions about vtkFixedPointVolumeRayCastMapper seem to indicate
that it can, however, so that is good news. I have some questions on
the class...

a) Is that particular module compatible with VTK 4.4? In other words,
could I download just that module and make it work with the rest of my
VTK 4.4 pipeline, or does it also require the use of the new pipeline
mechanisms and other changes implemented in the CVS version of VTK?

b) I have seen discussions on using this module to render two
independent scalars simultaneously... is it possible to render more
than two at a time? Is there a restriction on the number of scalars
that can be rendered?

c) Is there an easy explanation for not including this feature with
texture mappers? In our application, texture mapping is used for
'real-time' rendering, i.e. for swift user interaction. The option to
turn on ray-tracing is available for higher quality renders, but at
quite a high computational cost, so it would be nice if the same
result could still be achieved with multiple volumes...

Thank you for your answers,

Charles Boivin