RE: [Sripting] Removing particles via event?

["Vincent Fortin" <vincent.fortin(at)ubisoft.com>]

Hi Dan,

 

This sounds like a job for particle custom attributes.

Maya particles have built-in attribute for previous pos and vel which is handy.

 

I always remove particles by zeroing their AgeLimit. I don’t recall having any problem with that.

 

I did a similar setup in my spare time and faced the same issues regarding rendermap and motion vectors.

It wasn’t clear whether this was a bug or not. I think I ended-up comparing two position maps –as suggested by someone on this list- with the pixel parser to get the difference.

I say it’s a lot of trouble for what it is. Somebody also suggested using lightmaps which were not yet available in XSI at that time.

 

Hope this helps!

 

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From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf Of Dan Yargici
Sent: Thursday, December 13, 2007 7:38 AM
To: XSI(at)Softimage.COM
Subject: Re: [Sripting] Removing particles via event?

 

OK guys, so I've written a particle event now that will kill particles (almost) based on their velocity at birth - although I couldn't figure out how to use RemoveParticles to do the job from within a particle event.  I'm currently altering the particle's age so it only lives for one frame.

Aaaaanyway, what I need to be able to do is to emit based on the change in velocity between frames.  So when the surface stops moving (and only then), particles are flung off it...

Is it possible to query the particles velocities on the previous frame?  Anyone else managed to achieve this effect in XSI?  Somebody here managed it in Maya using regular expressions.  Makes you wince sometimes....

Thanks,

DAN

On Dec 12, 2007 11:10 AM, Dan Yargici <danyargici(at)gmail.com> wrote:

Coming back to this - does anyone know of a way to rendermap out Motion Vectors in world space?

Ideally I'd still like to be able to do something along the lines I mentioned in my first post....

Cheers,

DAN

On Dec 10, 2007 3:47 PM, Dan Yargici <danyargici(at)gmail.com> wrote:

Hi Morten, It's a sound idea, but it would be a knot in the pipeline and probably wouldn't be worth it for what it would add to the shot...

Cheers,

DAN

 

On Dec 10, 2007 3:36 PM, Morten Bartholdy < xsi(at)colorshopvfx.dk> wrote:

How about using a motionvector shader and try and hook emissions up to that? Might require you to rendermap a texture sequence but it seems to me you could find a clip value and emit particles when the values are above it.

 

Morten Bartholdy
3D & VFX Artist

 

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

From: Dan Yargici

To: xsi(at)Softimage.COM

Sent: Monday, December 10, 2007 4:21 PM

Subject: [Sripting] Removing particles via event?

 

Hi all,

Is it possible to remove particles from a cloud using a Particle Event?  The ParticleCollection object doesn't seem to support it....

Basically, I'm looking for a way to only emit particles based on the velocity of the object (or it's deformations).

I would have preferred a SCOP that would update a weightmap on the geometry which I could then use to drive the emission, but it doesn't seem doable....  The way I'm trying to approach it now is to emit all the particles and then clean out the one that are age=0 and velocity below a certain threshold - thus giving the impression that they were never there in the first place... seems like a really crappy way to be doing this, I know - if anyone has any suggestions I'm all ears!

Cheers,

DAN