particles emitting particles - inherited dynamics

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Old 02 February 2012   #1
particles emitting particles - inherited dynamics

Hello friends

I have a particle system that has 3 ramps controlling opacity, radius, and incandescence.
the ramps are run by a PP sine wave expression.

These particles are being used as an emitter for a second particle system.

I want these children particles to inherit the initial opacity, radius, and incandescence values of the parent particle, than decrease in value as they age. (think retinal after burn)

To do this I have been trying to use diagonal ramps (rotated to the lower right hand corner with place2dtexNodes). I created a PP float attribute (opacityPipe) on the children particles which has a creation expression = to parentParticleShape.opacityPP and a runtime bfd expression parentParticleShape.opacityPP=parentParticleShape. opacityPP.

I have been plugging the out value of opacityPipe into the u coordinate, and the child's ageNormalised into the v coordonate of the arrayMapper.

Despite all of my fiddling I can't seem to get this set up to produce the results I want. I have even tried a setup using attributeTransfer node in Peter Shipkov's soup.

Am I missing something?

any advice would be greatly appreciated!!

Last edited by rondobloodcannon : 02 February 2012 at 11:33 AM. Reason: clarity
Old 02 February 2012   #2
Rather than using an emitter, you can use the emit command. Gather the parent particle attributes, then use "emit" to spawn the new particles with those attributes.
Old 02 February 2012   #3
Smile Thank you!

Thank you! It seems like I am on the right track now. The particles seem to be inheriting their attributes properly.

The only problem now is that at around frame 20 the "parent" particles stop, begin stuttering increasingly fast in - and + directions, and than shoot out in every direction.

When I rewind the animation they do not return to their initial state.

Removing "parentParticleShape.position" from the "$pos" variable and replacing it with a "1" seems to fix this odd reaction.

I need the parent particles to retain their original motions while emitting from their current positions. Any ideas as to what I am missing?

additional info:
runtime before dynamics
seed (parentParticleShape.particleId);
vector $pos = parentParticleShape.position;
float $rad = parentParticleShape.radiusPP;
float $opc = parentParticleShape.opacityPP;
float $inc = parentParticleShape.incandescencePP;
emit -object childParticleShape
-pos ($pos.x) ($pos.y) ($pos.z)
-at radiusPP -fv $rad -at opacityPP -fv $opc -at incandescencePP -fv $inc;

The child particles are not affected by fields and are attached to a separate nucleus.

The parent particles emit a force field that interacts with an invisible attractor particle that also emits a force field.

no particles are set to collide.

increasing the substep settings and removing the initial state does not seem to help.
Old 02 February 2012   #4
Thumbs up

fixed! Apparently using the position attribute was changing the way the parent particles were interacting with my drag field. I lowered the magnitude and their motion returned to its normal state.
Old 05 May 2012   #5
Just gotta say that I used this emit method with great success today!
Thanks for the easy radius control tip!!!
Yay, CG talk.
Old 05 May 2012   #6
you can all this in SOuP with just one intermediary node. Goodbye emit command.

Last edited by Aikiman : 05 May 2012 at 09:24 PM.
Old 06 June 2012   #7
I need to turn nparticles into particles, can this be done with SOuP?
(one on one, "convert" nparticle into particles)


"No Bucks, NO Buck Rogers!"

VFX rule no. 387
# Just redo it!

Old 06 June 2012   #8
Originally Posted by Als: I need to turn nparticles into particles, can this be done with SOuP?
(one on one, "convert" nparticle into particles)

Not really, the internal data is completely different with a whole lot of connections going through Nucleus. I mean you can apply particle to particle position but that makes the second particle non-dynamic. What exactly are you trying to do?
Old 06 June 2012   #9
Have loads of scripts which work with particles, but not nparticles.
Also some plugins as well (like multitool).

"No Bucks, NO Buck Rogers!"

VFX rule no. 387
# Just redo it!

Old 06 June 2012   #10
Two things, Aikiman I just saw your post and just started using SOuP less than a week ago. Really loving digging into the example scenes. Just for educations sake what is the one intermediary SOuP node that I should look to instead of relying on the emit command? Attribute Transfer? I was using the emit command to set customPP attributes as well as the standard radius.
Again, just looking to tap into your crazy mad SOuP skills...I can't thank you enough!

The second thing, about converting nParticles to particles. For things like Radius, Color...anything that nParticles has a ramp controlling by default, you will need to create an expression to control those attribute on regular particles. Of course, you can't get regular particles to collide with each other so that kind of thing won't be able to be transferred. And rotation information will need to be generated as well if you need that...I guess I am saying it can be tricky to convert...but not impossible depending on your setup. Let us know what kind of sim you need to convert and maybe we can help.
Let us know what these magic scripts are helping you do and maybe we can give you some options that work with nParticles.
Hopefully we can help!
**Edit, just checked out multi-tool...definitely stuff you can do with SOuP on any kind of particle***

Last edited by animatedfox : 06 June 2012 at 01:00 PM.
Old 06 June 2012   #11
Thanks animatedFox nice to see you have caught the SOuP bug! Yeah there is a node called pointCloudParticleEmitter and I created several scenes in the scenes folder for people like you to check them out - they were in the last update so I guess you have them already. If you have any questions about them then go to the forums and ask away, that way I can catch your questions whereas I might miss them here.

@Als I think you would need a script to do what you are asking not a node as such.

Ill offer my assistance also but I cant guarantee any quick results but if you PM me and give me an example of exactly what type of conversion you are looking for I will have a look. Im not sure about changing a cache file, thats another beast in itself.

Last edited by Aikiman : 06 June 2012 at 11:39 PM.
Old 06 June 2012   #12
Thanks for the research tip!
I've been making my way through the example files...good to know where to direct my meandering. Loving every minute of it!
Rock on.
Old 06 June 2012   #13
For converting particles, you can go the manual route and just copy everything over by hand from a particle to NParticle or vice versa..

<shameless Self plug>
If you've already got a cache you want to use, you can also use partioEmitter from my
Partio4Maya plugin suite to load NCache particles or PDC's into a new particle object

The partio emitter works like a cache reader to load up particles from whatever format you have
and emits them with attribute mapping to a new particle object. Since its being done at emission time, you are free to change things via expressions on any extra channels except things that you are mapping from the cache.

So for example, you can map position and velocity and then still set your rgbPP via expression or a ramp.

give it a shot, its still in beta, but we're using it in production quite nicely right now
if you're on windows you'll need either the zlib for XP64 (separate download) or the included zlib in the latest plugin archive from april.

</end shameless plug >

Hope this helps!
Old 06 June 2012   #14
I've already been there... but...

Any chance on plugin for 2011?

I know, I know...
Have you tried it with 3Delight?


"No Bucks, NO Buck Rogers!"

VFX rule no. 387
# Just redo it!

Old 06 June 2012   #15
Its possible come siggraph that I'll have compiles of partio4Maya for 2011-2013,
in addition to a new version with new features.

stay tuned.

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