Re: particle trails

["Ajit Menon" <xsiajit(at)gmail.com>]

Yeah I do have the awesome particle baking script. The tubes idea was something I thought of mid-process... (and it was only one darned shot that needed that approach) but  didn't have time to RnD.

I think one of the fallbacks of that method was that I would have needed to implement another stack of deformers on the tube to mimic the pretty perlin noise pattern that the auxilliary particles created...

and thinking on, almost seems like some sort of a cloth solution (phew! we really know how to dig our own graves with solutions... at least I do!)

As a freelancer, XSIMan isn't any sort of a solution... though I hope MR brings some options. Then again, am still ardently waiting for the new particle system...

 

cheers!
 

On 4/27/07, Vince Fortin <vfortin(at)gmail.com> wrote:

Actually the sum of all Peter's tricks should give something very acceptable!

Except for the 2d post process that will give unsastisfying results if your camera is moving.

 

For your information XSIMan now lets you do sub frame motion blur with particles, something that we still can't do in MR. Not everyone enjoys hacking RIBS for a living but at least Renderman allows you to do things -such as the link you sent- with a reasonable development budget.

 

If you can put your hands on Brad's awesome CGS Particle Plot tool you'll be able to plot all particle trajectories, use them as particle emitters and get a result very quick. If you want to implement you tube idea, half the work is done, you could then track an extruded circle on each of the animated nulls. Plus, each of them come with useful information like visibility, color, etc.

 

And finally, I would like to add that Softimage|Particles had exactly the feature you're looking for, builtin, about 10 years ago ;-)

 

Good w-e everyone!

On 4/27/07, Ajit Menon <xsiajit(at)gmail.com> wrote:

Hey peter

Thanks for the reply.

There's also an interesting shader called genie tail around.... but it quickly gets very render-intensive... especially for pretty, smooth trails.

Interestingly enough, talking abt the beam shape for paticles... it doesn't support lenght relative to per-particle velocity does it? I know maya has such a hardware function...

 

For the project above, I actually ended up using after effects' particular system to create a lot of the 'fixed' trails after importing 3d-null data... worked like a charm and even better, it was practically real time, even with paticle counts going into several 100,000. But it balked at the final step when I really needed to use the 3d system....

 

I'm def curious what the new particle system for xsi brings with it...

But for trails, I think systems like the renderman shader system seems like a good solution instead of having to spew out a million fine particles and vary them for different camera positions...

 

...then again, it also might be interesting to build a tool that, after baking particle xyz into curves, takes a tube and curve deforms while tracking to the original particle's XYZ.

hmmm.. painful for a lot of streams though! 

 

On 4/27/07, peter boeykens <peter_b(at)skynet.be > wrote:

there's quite a few ways to get trails from particles.

 

you can have the particles generate 1 static particle on each frame

you can plot the particle's curves and use those to create geometry

if you scale the particles quite big and change the shape to beam you get a streak

you can use beam shaped instances

in compositing there's frame averaging

you can add each frame on top of the previous one, and save it out like that before adding the next one.

 

those are the first I can come up with, there's more.

each has its own look and use.

 

admitted, what the page describes doesnt seem readily possible in XSI

 

oh, and if you slow down you animation you will get less gaps with the event emission.

not to say that sub-frame event emission isnt sorely missed...

 

 

 

----- Original Message -----

From: Ajit Menon

To: xsi(at)Softimage.COM

Sent: Friday, April 27, 2007 8:50 PM

Subject: particle trails

 

Does anyone know of a shader/ technique to render particle positional data?

I was recently on a job where I had to create comet-like paticle trails from a spheroid object, but the nature of the emission was such that I needed the secondary emission (via an event) to create the trail... and as far as I know, event emissions don't support sub-frame emssion... hence, however much I pumped up my rate/ tried to vary spread and inheritance, I would always get some form of a gap in the trails... and the idea was to try to create smooth, pretty trails like the ones we see in a windows (or itunes) visualizer.

Then I came across this site which indicates a renderman technique to render positional data:

http://www.fundza.com/mtor/rib_box/particles/index.html

 

Seems like a nice way to go and I was wondering if anyone had tried something like this or better still, just knows the sytem better than I do... (then again, maybe it's already in the new upcoming XSI p-system?)

 

Cheers!!!