[vtkusers] How to visualize thousands of actors with good performance

[Affolter Martin]

Hi Björn

Thanks for your reply. The example I used for comparison has about 8000 actors, but we also have bigger models with several 10'000 actors. I honestly doubt, that our problem is OpenGL related. We've been using VTK 4.2 and VTK 4.4 for some years now and have never had performance issues so far. Those only emerged after we moved to VTK 5.6. Both versions use OpenGL, but only with 5.6 the interaction performance is poor.

So far I've tried static mappers and/or immediatemoderendering with little success. Right now I'm looking for a way to file an example that I can provide to those willing to look at it. OpenSceneGraph sounds interesting.

Regards
Martin 

Von: "Björn Zehner" [mailto:bjoern.zehner at ufz.de] 
Gesendet: Dienstag, 28. September 2010 18:00
An: Affolter Martin
Cc: vtkusers at vtk.org
Betreff: Re: [vtkusers] How to visualize thousands of actors with good performance

Hello Martin,
 
how many thousands of actors do you have? I am asking because rendering performance is not only limited by the number of vertices and triangles you have but by the number of objects too. This has more to do with OpenGL than with VTK. I think this is explained in more detail in:
"Cebenoyan, C. (2004): Graphics Pipeline Performance. In: GPU Gems, Edited by Randima Fernando, Addison Wesley, Boston"
I believe that NVidia has made this available online.
 
If this is your problem, than you need some datastructure that allows to efficiently cull away the objects that are not visible (e.g. a quadtree). Are all objects (vtkActors) visible at the same time? If yes, you might need to make some assumptions, such as that the users can only pick objects that are near, and combine these culling techniques with Level Of Detail techniques. I am not sure if such an implementation can be done with VTK, may be you need a scenegraph that is targeted at rendering, such as OpenSG or OpenSceneGraph.
 
Kind regards,
Björn Zehner
 

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