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Old 25-04-2005, 05:00 PM   #1
azimuth
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Exclamation Stopping an emitter mid animation?

I have a short animation running for 70 frames, for frames 20 - 30 I would like to have a particle emitter.... emit some particles

I can get it to start emitting at frame 20, but it keeps emitting all the way through to frame 70. Is there a way I can stop the emitter at frame 30?

example
The look i'm going for is a bullet hitting the ground and sending up a finite amount of dust/earth. At the moment the dirt just keeps on coming for the whole length of the animation.

Kind of an urgent problem (needs to be solved by 2morrow)!

Thanks guys
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Old 25-04-2005, 05:54 PM   #2
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hi can you not just key the option that makes the particles emit so up until frame 30 it is emitting then key the birth rate (or whatever it is, not really up on maya's particles) to go to to 0 on frame 31 the particles should stop emitting
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Old 25-04-2005, 07:08 PM   #3
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Thats kind of what I have been going for so far yeah.

As people can guess I'm not to hot on particles yet, so all I can see so far that could make a difference are:

1. I can find the attribute that sets when the emitter should begin emitting, but there doesnt seem to be one that sets a frame for the emitter to stop

2. Rate / partilces per second. This varies how much comes out. I need it to be a high figure so in render you see a good sized 'puff' of dust coming up.

I need a sudden burst of many particles, that stops quickly afterwards - are particles even the best job for this?

Thanks as always
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Old 25-04-2005, 07:18 PM   #4
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if the rate gets turned down to 0 what happens if no particles come out them key that on the frame you want it to stop on and key the original setting on the frame before
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Old 25-04-2005, 08:02 PM   #5
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ok just did a quick test and as I said up above if you key the rate as
Frame 29 = 100 (or whatever you have)
Frame 30 = 0

At frame 30 it will stop emmitting particles but the particles will still drift about for a while so to slove this follow the next part

Go into the particle shape node goto lifespan attributes and intally put you settings to:
Lifespan mode = random range
Lifespan = 1.
Lifespan random = 2.
General seed = 0.

If you don't like how fast they "die" then change the lifespan and the lifespan random

Hope it helps
Rob

Last edited by sspikedudley : 25-04-2005 at 08:09 PM.
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Old 25-04-2005, 08:16 PM   #6
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Holy Crap! That worked so well you wouldnt believe!

I never realised you could key frame particles like that.

Thats a huge help, I owe you a

Cheers!
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Old 25-04-2005, 08:19 PM   #7
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you can key almost every attribute if not all of them.

I will hold you to that beer

Let me know how it goes

Rob
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Old 27-04-2005, 08:15 PM   #8
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I did a similar animation but with a guy coughing and sending up dust...

a better method rather than using an expression or keyframes is a particle collision event

use a particle collision event found under your particles menu make sure that the type is Emite and (optional)Random # Particles is checked... then set your Num Particles, the spread, and your target particle (which requires a second particle to be created) and lastly make sure that Original Particle Dies is checked....

in your (name)Shape take your conserve down to 0 and everything else should really stay at default.....also setting the lifespan mode and other lifespan properties will help in making the particles die off as they should as sspikedudley already stated but with one change and I will tell you why

lifespan mode = random range
lifespan = 1
lifespan random = no higher than lifespan and no less than 0

the reason why you set the lifespan in that manner is because what happens is the solver the particle uses will add 1 and subtract 1 to the lifespan to give the total lifespan range 0 to 2 (lifespan - lifespan random; lifespan + lifespan random).. if you set the random any higher than the lifespan then you risk taking the range into negative which will most likely (not all the time if you're lucky) make the particles go in the wrong direction instead of letting a gravity field take over.

now take note, your target particle does NOT need an emitter and with a particle collision event you do not need an expression....

see if that works out better for you
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Old 28-04-2005, 04:24 PM   #9
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Well I had a quick go at your suggestion Razor, and it certainly worked, although roughly for a first attempt - with a bit more practice I think I could get it spot on - thanks for the suggestion.

As for a little update - the animation I was working on was for a rough demo reel to show a prospective MSc tutor for a 3d and multimedia post-grad course. Showed the guy my work and he seemed happy and offered me a place :bandit: . Now as long as I can dig some up from somewhere I'm good to go.

Cheers as always to everyone who answers questions here, and to sspikedudley for getting my animation past that sticky point and onto a CD
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Old 28-04-2005, 04:34 PM   #10
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yeah the particle collision event (PCE) is by no means easy it takes a little work to make it look good as with any aspect of 3d art, also remember using the particle textures too that will help a lot in making your stuff look good...

Also in the section Per Particle (Array) Attributes section there are some items there that are particularly helpful...lifespanPP and goalPP are two that you may use the most....you can set expressions before runtime, after runtime and even on creation... you can also add in attributes in that section also by going down to the next section Add Dynamic Attributes... you can add an attribute, the color, and opacity you can add as per object (all particles), per particle(one particle at a time) or a shader...

The one thing I like about using the tools like the PCE is you don't have to worry about keyframing your attributes as much as you would be doing without the PCE.....

Hope to see your dynamics soon
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