[vtkusers] concept of visualizing large datasets (no ParaView)

[David E DeMarle]

On Tue, Jun 6, 2017 at 3:19 PM, Trevour Spencer <trevourspencer at gmail.com>
wrote:

> Dear VTK experts,
> I'd like to solve a problem with visualizing datasets that are too large
> to be rendered fluently on a single node.
> We have datasets that have been distributed with PT-Scotch across ~10-100
> nodes of a MPI cluster (each node has a GPU, but for now we are rendering
> CPU only.). A vtkUnstructuredGrid has been created on each process to
> visualize the respective fraction of the data that is stored in this
> process. So far, we have been successful.
>
> How would I create a composite image that combines all data from all
> processes? Apparently http://www.vtk.org/Wiki/VTK/
> MultiPass_Rendering#Parallel_rendering gives some ideas, and the example
> http://www.vtk.org/gitweb?p=VTK.git;a=blob;f=Filters/Parallel/Testing/Cxx/
> DistributedDataRenderPass.cxx is perfect for distributing the points of a
> small dataset across 2 processes and rendering the combined image.
>
> What I cannot find out with these examples is:
> How do I proceed, if the data *are* already distributed across the
> processes? I cannot gather all data on process id #0 (too large) to pass
> them to a vtkDistributedDataFilter as in the example above. How should the
> DistributedDataRenderPass.cxx be modified to run with initially distributed
> data?
>
> I appreciate your thoughts
> Trevour
>
> ps: Finding a solution without ParaView is a requirement from our IT side.
> We can't argue with them :(
>
>
boo! ;)

See tests and examples reachable under doxygen for :
http://www.vtk.org/doc/nightly/html/classvtkCompositeRenderManager.html
and
http://www.vtk.org/doc/nightly/html/classvtkCompositer.html
for orchestrating the synchronous independent pipelines and depth
compositing respectively.

Pretty soon you will want to swap out any VTK native compositor for IceT
since that is better optimized and tested.
For ideas on how to go about that see:
http://www.vtk.org/Wiki/VTK/MultiPass_Rendering_With_IceT

Bit of advice - although it can be a chore to compile/install ParaView it
can also be a chore to develop something from scratch.

good luck with either path.
cheers

David E DeMarle
Kitware, Inc.
Principal Engineer
21 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4909
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