[Paraview] Animation with sudden large intervals between consecutive frames

[Tom Fahner]

Dear all,

For some reason I noticed that ParaView has some large intervals between
writing a PNG for consecutive frames of an animation. Normally there is
about one minute between the timestamp of two PNGs, but sometimes there is
suddendly a gap of 8 hours:

 141K Jan 13 15:56 New_Volume_.0118.png
 141K Jan 13 15:58 New_Volume_.0119.png
 139K Jan 13 15:59 New_Volume_.0120.png
 139K Jan 13 16:00 New_Volume_.0121.png
 138K Jan 14 00:34 New_Volume_.0122.png
 139K Jan 14 00:35 New_Volume_.0123.png
 139K Jan 14 00:36 New_Volume_.0124.png

There are multiple occasions where these large intervals happen but this
does not happen at a regular interval of the animation. There does seem to
be a relation with the amount of memory that is used, since there is a
sudden decrease in memory used right after "Jan 14 00:34". Below I will
describe my animation and setup. I hope anyone can give an explanation for
the behavior.

During the weekend I have created an animation of a mixing tank using
volume rendering of the concentration of some chemicals in the tank. It is
a reasonably large CFD simulation performed with OpenFOAM. There are about
15 million cells (tetrahedrals and prismatic layer), but not extremely
large. I saved the concentration every 0.25 seconds for a 120s simulation.
We have ParaView 3.98.0 installed on this machine and it was the only
program running at the time. I have made the animation with ffmpeg after
ParaView made the frames as consecutive pngs. Besides the volume rendering
of the concentration, the walls of the tank where shown with a fixed
opacity of 0.3 and the internal structure (some rotors and baffles) where
present as well. Although the simulation use the MRF concept, I did mimick
the rotation of the rotors using the transform filter. Using the "cool to
warm" preset for visualization I could nicely set the opacity to 0 when the
concentration was in the allowed range and it showed red in case of too
high concentration, of blue when too low. The resulting animation is
satisfactory, I just wonder what can be done to make sure these large
intervals between writing images do not happen.

Hope someone can help, if you need more information, please let me know.

Regards,
Tom

-- 
T.C. Fahner
e: tom.fahner at gmail.com
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