[Paraview] ParticleTracer particle lifetime

[Berk Geveci]

I got it. I think that the correct way of doing this would be:

1. Seed particles
2. Integrate 1 time step
3. Kill particles that are older that threshold
4. Connect particles to generate streaklets
5. If time step % n == 0, update seed source randomly
6. Go to 1 if time step left

Does this make sense?

-berk


On Tue, Jan 14, 2014 at 3:17 PM, Ryan Abernathey
<ryan.abernathey at gmail.com> wrote:
> Berk,
> That might be the correct interpretation for the first video, which I think
> uses a steady (i.e. not time-dependent) flow field. For steady flows,
> streamlines, streaklines, and trajectories are all identical.
> But if you look at the second video, I think you can see that they are
> plotting Lagrangian trajectories. My velocity data is time-dependent, so I
> think I need the trajectories.
> -Ryan
>
>
> On Tue, Jan 14, 2014 at 2:47 PM, Berk Geveci <berk.geveci at kitware.com>
> wrote:
>>
>> 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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