[vtkusers] debug volume rendering performance with volumepro1000

[Dr. Daniel James White PhD]

Hi All,

We have recently acquired a volumepro1000 volume graphics board to 
speed up the volume rendering of our large data sets in MayaVi,
which is a VTK application for data visualisation with a user interface 
written in python.

Using vtkVolumeProMapper in place of vtkRayCastMapper or 
vtkTextureMapper2D we do indeed see an increase in rendering 
performance.
The raycastmapper is much slower than the volmepromapper, but the 
TextureMapper2D is only 2 or three times slower.
We get frame rates between 10 and 1 frame per second using the 
volmepromapper.
This board should give 30 fps!

Our data sets are smaller in all 3 dimensions than the  512x512x512 
limit that I believe the volumepro1000 board can handle with its on 
board memory,  so the data should not be "paged" by the board.

The board is in a short/33MHz PCI slot, not the recommended long/66MHz 
slot recommended.
Would this cause the slow performance? I think I saw that it might only 
give a 10% performance it, but I could be wrong.

Otherwise, what is the best way of going about finding bottlenecks in 
the VTK and hardware rendering pipeline?
How do I actually test the speed of each part of the pipeline to find 
the bottleneck?


Possible places might be
1 PCI bus between the processor and the volumepro1000 card,
2 python,
3 VTK c++,
4 ATIRadeon8500 graphics card,

One extra bit of information I have is due to the volume pro board 
having a small defect which causes it to squeak every time the display 
is refreshed/redrawn. So I hear a noise for every frame update.
It kind of sounds like the volumepro1000 board is only rendering as 
many frames per second as the graphics card is displaying (or at least 
doing something every time the display updates..... the noise comes 
from a power converter apparently).
Is this because that is the fastest frame rate the volumepro1000 can 
handle under these conditions (it should be faster according the the 
documentation), or is it that VTK is not sending the rendering 
instructions to the volumepro1000 board fast enough, or something else?

My system is redhat linux 8, VTK and MayaVi from very recent CVS, 
athalon 1.5GHz processor, ATIRadeon8500, volumepro1000 512MB in 33MHz 
PCI slot with linux vli3 library.

Any debugging suggestions very welcome!

cheers

Dan

Dr. Daniel James White BSc. (Hons.) PhD
Cell Biology
Department of biological and environmental science
PO Box  35
University of Jyväskylä
Jyväskylä FIN 40014
Finland
+358 (0)14 260 4183 (work)
+358 (0)414740463 (mob)

http://www.chalkie.org.uk
dan at chalkie.org.uk
white at cc.jyu.fi