[Paraview] Rendering performance issue?

[Albina, Frank]

Dear ParaView users & developers,

I am trying to reduce the time spent in performing generic 3D surface rendering. A lot has been achieved by using ParaView driven by python scripting already but actually I'd like to achieve more. At the time being, all rendering is performed using CPU rendering with the MESA libraries and I have started investigating if it could be worth performing the rendering using GPUs instead of using N CPUs in parallel.

For the purpose of checking the GPU performance over CPUs, I have devised a simple benchmark with a python script which drives the surface rendering. The script performs the generation of 60 images and dumps them onto disk in JPEG format. When performing this task, I have been tumbling upon the following rendering times for the generation of the aforementioned 60 images, using different versions of paraview on an "old" workstation, which is my guinea pig for this benchmark:

Paraview 3.8.1

Paraview 3.10.1

Paraview 3.12.0

Paraview 3.14.1

138.12s

591.06s

592.53s

594.10s


What is striking is that the rendering time is 4 times less(!) with PV v3.8.1 than with all subsequent versions. I had already noticed something similar when running MESA on dissimilar architectures, but I assumed that the culprit were the MESA libraries used. Here, the HW and libraries are the same, so I am enclined to believe that I am missing something here in the general rendering settings which do not affect PV v3.8.1 but induce a big performance hit for all PV versions above 3.10. Is anybody aware of rendering settings which could induce such a performance difference?

BTW, for each rendering, a window opens with the OpenGL tag in the window title bar, so I am quite sure that I am not using any SW rendering, all the more as all the PV versions I have compiled have VTK_OPENGL_HAS_OSMESA set to off.

A few more details concerning the test I have been running:

 - Workstation: Linux workstation with SuSE SLED 10
                         2 x Intel Xeon Dual core 5160  @ 3.00GHz
                         2 x NVIDIA Quadro FX3500 (NV71GL chipset)

 - Paraview version 3.8.1, 3.10.1, 3.12.0 and 3.14.1 were compiled with OpenGL support, Qt v4.6.x, python v2.7, OpenMPI v1.4.x using the GCC compiler v4.5.x.

 - The script is run using pvpython (and not pvbatch) in order to force the assignement of the graphics card:
    pvserver -display localhost:0.0
   Then the rendering script runs with pvpython from the command line. Within the script,  a Connect("localhost",11111) forces the connection to the pvserver running on localhost.

Any suggestions welcome.
Best regards
Frank Albina.
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