[Paraview] ParticleTracer particle lifetime

[Ryan Abernathey]

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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