Sprites popping in and out?

[phalimjinx]

Me again.
I have a smokestack that I am making and I have one particle object that emits a particle object and then it also emits another particle object at the end of it's life using a ramp on ratePP. Both of these emitted particles are sprites and I am having a problem where one particle object keeps snapping in and out. I am assuming this is a problem based on the sprites occluding one another. It looks like a problem that would be solved by checking "depth sort" but as I said, it's 2 different particle objects. I have checked "depth sort" in both particle objects, and then each particle separately and the problem still persists. (I need two separate particles because the first particle needs to be smaller and the second particle needs to be larger to simulate the spreading out of the smoke.)

Any ideas how to fix this, or a way around it in maya that might allow me to fix it compositing?
Thanks,
-P 

[joojaa]

Are you sure this is the problem. What if the objects actually order that way? It might also be caused by the fact that the movement actually does this*. In this case just kill the individual offending particle.

(I need two separate particles because the first particle needs to be smaller and
the second particle needs to be larger to simulate the spreading out of the smoke.)

You dont need 2 separate particle objects because you particles have 2 different properties. You can mix any number of any size any image things in ONE particle system. In essence if you can do some thing with two systems you can do it with one, period.

However the real problem might be the range of the near far clipping planes. See if you can bring the clipping planes closer together you get more depth resolution that might make this go away (because in essence if the 2 sprites quantize at exact same spot). But i suppose you can allways use a software render instead.

• in which case maya is doing the right thing even if its undesired consequence.

[phalimjinx]

Okay Joojaa,
Thanks again for your help!

I'm not sure if it's the movement of the sprites that's causing it because when the popping occurs it seems to be the whole particle object (or at least many particles.) and the size of this "popping cloud" is larger than the frequency of the turbulence that is moving them. So it doesn't really make sense to me the whole big group would be moving together like that.

I adjusted the clipping planes  (near 1.0 and far 150.0) but the popping is still happening.

I am a little confused HOW I could use just 1 particle object instead of 2 and get the same look. Let me explain in more detail the setup: There are currently 3 particle objects. Particle1 is the emitter particle which doesn't render. It emits particle2 as it rises to form the main plume of the smokestack. At the end of the emitter particle's lifespan it then (in addition to emitting particle2) emits particle3 to simulate the spreading of the smoke. Particle3 has a larger spriteScale, a slower spriteTwistPP, a smaller conserve value, a longer lifespan, and a slower fade out (opacityPP) and the two particles (particle2 and particle3) are connected to two different turbulence fields.

Normally I would write a conditional statement using the particleId to set the different attributes, but I can't use the particleId if they were both the same particle object because particles from the particle2 object are still being emitted when the particle3 object is emitted so I can't just use:
if (particle2.particleId > $someNumber)  
{}

since that would get me some of the current particle2 at the bottom of the smokestack instead of just the big particles at the top (what is currently particle3). However, even if I could think of a way to determine if a given particle should be a big one or a little one (maybe link particle1's current normalized lifespan and after the normalized lifespan is greater than .7 or whatever, make it choose to be small or big since they both are emitted at that point? Might work, though I'm a little hazy how to go about that), I'm not sure how to adjust the conserve value (I didn't see conservePP on the list) and I'm not sure how to use the two different turbulences. is there a way to link particles to fields on a per-particle basis?

If you could explain HOW I might get particle2 and particle3 to be just one particle, that would be awesome! I really think that would solve the problem.
Thanks again Joojaa. You've saved my job a couple times now! You're great!
-P