Re: Barnes-Hut treecode (was Re: Galaxy Interaction Simulations)

Chris Metzler (
9 Mar 1994 00:08:58 GMT

In article <2lileh$>, (Andy Boden) writes:
|> 3) How do folks visualize the output of these simulations (I'm
|> X-windows based, so I guess the question should be read with this in
|> mind). In this case I think I can solve this problem with tools I
|> already know about. But again it's stupid to screw around with
|> something that's not quite right if the "right tool for the job" is
|> sitting out there somewhere on an ftp site.

Well, first off, I should say that I don't work with a copy of the
Barnes-Hut treecode; or any other treecode, for that matter. I use
an N-body + hydro code, where the hydro is done by SPH (which Chris
Mihos has already spoken of), and the N-body by a particle-particle /
particle-mesh scheme. It's a little bit older approach than treecodes,
but perhaps more appropriate when simulating structures which don't
occupy a large fraction of the simulation volume. But that's controversial.
Anyway, I can talk about that if anyone cares.

As for visualization, if all you're interested in is the physical
location of the particles in the simulation, then if you understand
the format of the output files, it should be easy to write a program
that can read simulation output and write files containing particle
x-y positions produced either by projecting the entire volume onto a
plane (from some given perspective/pair of angles), or by taking a
wedge out of the volume and projecting the contents of that wedge onto
a plane. With a little ingenuity, you can get fancier -- writing
velocities in the plane as well, and using whatever plotting package
you use (I use sm) to attach arrows to the particles showing
direction and magnitude of motion, or whatever.

But if you really want to get fancy, then 3-D color visualization packages
such as AVS or SGI's Explorer are the way to go. But there, you're talking
about lotsa bux.

Chris Metzler
Department of Physics, University of Michigan		313-764-4607 (office)
Randall Lab, 500 E. University				313-996-9249 (home)
Ann Arbor, MI  48109-1120 USA     E-MAIL:

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