Each particle is parallel but not necessarily coplanar. Specifically, they all
turn to face the view, but can be at any location.
This is somewhat different than the billboard behavior. Billboarding will turn
to face the ViewPoint, which means that for each billlboard they must comute
there own rotation because the rotation is related to their location. The trick
with particles is that they all turn to be MATCH the View's rotation, so it only
needs to be computed once. Lemme me know if you would like more details.
If I understand you correctly, I believe the particle cylinder you describe
would work fine.
"Yazel, David J." wrote:
> Shawn:
>
> Does each particle in the system have to be coplanar? Would it be possible
> to assemble the particles in a cylinder around a point and rotate the
> particles, keeping each particle facing the image plate?
>
> Dave Yazel
> Cosm Development Team
>
> > ----------
> > From: Shawn Kendall[SMTP:[EMAIL PROTECTED]]
> > Reply To: Discussion list for Java 3D API
> > Sent: Tuesday, October 24, 2000 9:24 PM
> > To: [EMAIL PROTECTED]
> > Subject: [JAVA3D] Particles System and GeometryArrays
> >
> > <<File: particle-by-ref.jpg.jpe>>
> > Ok, kudos to Uma and Kelvin for helping me work through this one!
> > Thank you, thank you.
> >
> > Here is a short explanation of what we are doing and the results.
> >
> > We implemented a "Particle System" (I prefer Manager, it's not really a
> > system) in Java3D.
> > Our first attempt was simple using TransformGroups, Shape3D's and
> > behaviors for every particle object.
> > This works, but of course, is way to slow. However, it is no too slow
> > because of Java3D or something else, it is simply because using many
> > Transforms and Behaviors is going to be expensive.
> >
> > In gaming, a particle system is usually two classes may be even one, the
> > particle, and the particle updater or manager.
> > We reviewed several straight OpenGL and D3D particle systems before
> > implementing our second system. All of the systems we found only use a
> > Quad or TriStrip for each particle. When that is the particle's geometry,
> > optimizations can be set up to take advantage, so only TWO full vector
> > transformations need to be computed for the entire system to be
> > "BillBoarded" correctly. So we knew we would try this technique using no
> > TransformGroups, one Shape3D, and one Behavior. To do it right we needed
> > to get as close to the GL_TRIANGLE level that we could in Java3D. With
> > help from Uma and Kelvin, we have implemented two different version, one
> > using the direct set methods in GeometryArray and one using the by-ref
> > mode of GeometryArray.
> >
> > First off all, both methods where orders of magnitude faster than the
> > multiple TransfromGroup/Shape3D/Behavior method. We still had some
> > rendering problems, but that is practically fixed in the pre-beta.
> > Second, once the by-ref method was up and running we got another 100%
> > increase in frame rate (for our particular particles test case anyway and
> > on a GeForce H/W T&L). Needless to say it was much faster and looks
> > great!
> >
> > Now making a particle system like this is not nearly as versatile as the
> > full TransfromGroup/Shape3D/Behavior system. It can only do billboarded
> > and usually alpha textured quads. This is the classic particle engine in
> > games. Sometimes you need real geometry that had independent rotation,
> > etc. I call that Debris (from my simulation days) so we are planning to
> > keep the original system and improve it to complement the particle system
> > when that kind of look is wanted.
> >
> > I attached a picture for fun.
> > For those interested, I plan on writing all of this up more formally with
> > code and benchmarks soon.
> >
> > --
> > ___________________________________________________________
> >
> > Shawn Kendall Full Sail Real World Education
> > Course Director 3300 University BLVD
> > Real Time 3D for Gaming Winter Park FL 32792
> > [EMAIL PROTECTED] http://www.fullsail.com
> > ___________________________________________________________
> >
> >
>
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--
___________________________________________________________
Shawn Kendall Full Sail Real World Education
Course Director 3300 University BLVD
Real Time 3D for Gaming Winter Park FL 32792
[EMAIL PROTECTED] http://www.fullsail.com
___________________________________________________________
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To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
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