RE: Set Interparticle Avoidance per particle?

[Bradley Gabe <withanar(at)stanwinston.com>]

Sorry, I'm late to the thread. I had to do something entirely similar, and also using XSI particles for a swarm effect.
The trick I came up with was to do a 2-phase particle simulation before plotting to curves and doing a motion analysis:

1) I created a particle cloud by filling a volume using some interparticle avoidance, collision on the volume interior, and noise. The result is a swarming volume cloud, contained within a shape, sitting at my scene origin.

2) I deformed the first cloud on a path, and used whatever other deformers would work to shape the cloud and control its motion and timing.

3) I created a second cloud, then used the first cloud as a particle spring target. The second cloud is the one I used to generate my animation paths. By balancing between the spring force, viscosity, and interparticle avoidance, I was able to get the second cloud to look like a random flock, but also reasonably control its motion and overall shaping. Plus, I could use additional collisions and forces to influence it.

If you want to try this technique, make sure to include 100 or so frames for your second cloud to settle into its spring targets on the first cloud. Over the ramp in, turn the spring force very high in order to pull the particles into place, then relax them in time to start into the sim.

-Brad

> Just pinning again. Anyone has any input on this issue? Anyone ever had to
> deal with something similar?
>
> -----Original Message-----
> From: Mathieu Leclaire [mailto:mleclair(at)hybride.com]
> Sent: Tuesday, June 05, 2007 11:00 AM
> To: XSI(at)Softimage.COM
> Subject: Set Interparticle Avoidance per particle?
>
>
> Hi guys (and gals),
>
> I’m using Interparticle avoidance from the Interpart. tab of the Ptype for,
> well, obviously, keeping particles at a certain distance from one another.
> Now the thing is they keep a certain distance from one another depending on
> the radius setting but I want the radius to diminish once they reach a
> certain area so they can squeeze tighter together to pass through a more
> limited space through an obstacle. Can I change the radius per particle
> through a scripted event? Because now, all I can do is animate it from it’s
> age and hopping they arrive at the perfect timing which is quite difficult,
> annoying and limiting my options.
>
> Anyone has any suggestions on how I can deal with this issue? Or do I have
> to code my own interparticle avoidance function?
>
> Thanks for the feedback.
>
> P.S.:  Just a little side note, I’m sorry I’ve not been participating to
> this list very much lately. I’ve been quite busy. I’ll do my best to be more
> involved from now on. I admit I’ve missed our colorful exchange of
> information. :)
>
> Take care everyone,
>
> Warmly,
>
>
> Mathieu Leclaire
> R&D Programmer
> Hybride Technologies
>
> "Yesterday is history, tomorrow is a mystery, today is a gift and that is
> why it's called the present"
>
>
>
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-- 
Bradley R. Gabe | Senior Creature TD | Stan Winston Studio