[Paraview] ParticleTracer particle lifetime

[Berk Geveci]

Hi Ryan,

When I look at these  movies carefully, it looks like they are using
streaklines that are seeded for a short burst. It looks like they pick
a number of seeds each time step and start a streakline from each and
keep them active for a few time steps. Then those streaklines seem to
be killed eventually. It also appears as if they are playing with
transparency depending on the age of the streakline. Am I right?

-berk

On Tue, Jan 14, 2014 at 2:20 PM, Ryan Abernathey
<ryan.abernathey at gmail.com> wrote:
> Hello,
>
> I am continuing my ongoing quest to do something like this
> http://earth.nullschool.net/#current/wind/isobaric/1000hPa/orthographic=267.73,5.54,350
> or this
> http://www.youtube.com/watch?v=xusdWPuWAoU
> in Paraview using ***time dependent velocity vectors***.
>
> While the LIC plugin is very cool, it does something different. I followed
> the previous suggestion and tried to use the streamline filter:
> http://paraview.org/Wiki/ParaView/Custom_Filters
> Unfortunately that is not quite right either.
>
> The problem with the streamline filter is that it treats each timestep as
> completely independent and regenerates the streamlines whenever the velocity
> field changes. (This is the correct behavior: streamlines are defined by the
> *instantaneous* flow.)
>
> What we see in those videos are truly particle trajectories. In particular:
> - particles are seeded randomly (in space and time)
> - they leave a decaying trail (sometimes called a streaklet)
> - the particles disappear after a short lifetime
> This is the combination of ingredients I need to reproduce in paraview.
>
> The best candidate is clearly the ParticleTracer filter. However, I have hit
> a serious problem: it doesn't appear that this filter is able to make the
> particles "die" after a temporal lifetime. Compare the v 3.3 documentation
> http://paraview.org/OnlineHelpCurrent/ParticleTracer.html
> with the current documentation
> http://paraview.org/Wiki/ParaView/Users_Guide/List_of_filters#ParticleTracer
> In the old version, there was an option called "Termination Time" that is
> missing from the new version.
>
> Without such an option, the particles will never disappear, the domain will
> get more and more crowded, and the computational expense will grow with
> time.
>
> Let me know if you have any suggestions or if you know how to re-enable this
> Termination Time option.
>
> Thanks a lot,
> Ryan
>
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