[Paraview] ParticleTracer particle lifetime

[Ryan Abernathey]

Yes, that sounds very sensible!

Of course, the difficult part (for me, a relative noob) is to actually
implement those steps in terms of a Paraview pipeline. Or would you
recommend creating a new custom filter?

Unfortunately experimentation has been difficult because of the slowness /
instability of the ParticleTracer filter. Even with a very modest number of
particles (~10), I experience crippling delays when advancing timesteps.
Perhaps pre-generating the trajectories is the answer.

Thanks a lot for your suggestions.
-Ryan


On Tue, Jan 14, 2014 at 3:32 PM, Berk Geveci <berk.geveci at kitware.com>wrote:

> 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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