Particle Problem

# 1 21-04-2008 , 10:54 PM

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Join Date: Mar 2008

Location: Providence, Rhode Island

Posts: 5

I have a problem with particles. I have a volume emitter emitting particles along an axis, and I want to set the start frame of the particles to frame -50. Everything seems to work fine in Maya; the particles move when I drag the slider around or hit play, rendering the current frame is fine. However, when I batch render the particles do something strange.

It seems as if they’re being calculated from frame -50 to frame 1 but the particles never move from their position at frame 1. My keyframed objects move, the cameras move, but the particles are stuck in the frame 1 position.

I’ve tested this by setting the start frame for the particles to -1 and sure enough, they get run up two frames and never move from that position.

I’ve tried working around this problem by moving my animation to frame 50 and starting the batch render at frame 50, but the exact thing occurs. The particles in frame 50 are positioned correctly but they never move.

Any help with this would be appreciated.

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# 2 22-04-2008 , 12:13 AM

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Join Date: Sep 2002

Location: Minnesota, USA

Posts: 3,709

Ok, before I try to get deep into what might be the problem(s), lets start with the very basics ok?
Cool user added image

When you create a particle object or an emitter emits a particle object, Start Frame is set to 1.0, by default. The value is the duration of a single frame in the current setting for time units.

Now this is the important part:
If you change the time units setting, you must set the Start Frame to the correct initial value so that Maya computes the start time again.
An emitted particle object accepts emitted particles only at frames greater than or equal to its Start Frame.

For example, to emit particles at frame number -5, set the Start Frame of the emitted particle object to -5 or less.

So, have you made sure that you setup your particle object/emitter like the above?

Double check and let us know, so we can proceed with other ideas user added image

Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com

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# 3 22-04-2008 , 12:35 AM

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Join Date: Mar 2008

Location: Providence, Rhode Island

Posts: 5

It's definitely set up that way.

I'd just like to say thank you for the help, by the way. The degree project crunch is upon us and you are most definitely my saviour.

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# 4 22-04-2008 , 02:35 AM

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Join Date: Sep 2002

Location: Minnesota, USA

Posts: 3,709

Ok, before I hit the hay for work, I ran a test of my own using the setup you described in your first post.

....sadly, my shot batch-rendered just fine user added image

So, no help to you there.

PS, I'm on Maya Unl. 8.5

Alright, before we troubleshoot, I want to warn you that there may be a "worst-case" possibility that I may have to ask you to email me your file so I can have a look at your settings just in case there is something small we may have missed user added image

Trust me, it happens.
...just wanted to warn ya first.
If this is not possible, then we may have to start over from scratch.

Anyhoo.. Since you say that your shot is working fine for you in the viewport by rewinding and hiting the play button, I first want to have you try making a particle-cache of your sim, then try rendering your shot again.

This essentialy tells maya to ignore the math of the simulation, and simply render the cached particle-positions.
It's just like baking any other keyframe in maya user added image

If you need help on doing that, check the Dynamics Help Docs, or just lemme know.

See if that workes for you before we go to the next step.

Good luck! user added image

Also, just a small pointless FYI in case you didn't already know:
Always remember that Maya will only play-back your particle sims correclty and consistently when you first rewind by clicking the left-most playhead button (the rewind to frame 1 button) on the lower-right of the Maya gui EVERYTIME you want to playback your shot user added image

You can start at frame one and scrub forwards, but once you go even ONE frame backwards, without a particle-cache to derive a previous-particle-position reference from, maya will have no way of knowing what you want your particles to do, so crazy things will happen, including possible file corruption user added image

Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com

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# 5 22-04-2008 , 06:05 PM

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Join Date: Mar 2008

Location: Providence, Rhode Island

Posts: 5

If it ultimately comes to file swapping, I wouldn't be opposed. But, anyway, yeah, caching the particles to disk didn't solve the problem. Oh, I'm using Maya 2008 Unlimited.

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# 6 22-04-2008 , 07:35 PM

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Join Date: Sep 2002

Location: Minnesota, USA

Posts: 3,709

Hmmm, the fact that you cached the particles and it still didnt work surprises me a bit, as that is usualy the LAST step in troubleshooting.

Also with the file being v2008 is going to be a problem for me, as I only have that version at work.

So, how complex is the shot?
Is it something we can recreate from scratch for ya maybe?

Just throwin out ideas user added image

But man, thats REALLY weird that it didnt render after caching it.
(as thats the final troubleshooting step that Autodesk support will tell you to do as well, hehe)

Anyhoo, can you attach, or PM-me your file anyway so I can take a look?

Thanks user added image

Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com

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