View Full Version : scaling particle size down to 0 over time

08 August 2008, 01:17 PM
I have a pflow system that is using instanced geometry for its shape. I had the particles dying off with a delete by age operator. I want that same effect of them dissappearing, but I want them to shrink down to nothing over time. Anyone have any ideas on how to do that?

08 August 2008, 02:20 PM
use a scale operator and animate the scaling to 0. over the particle life.

so you obviously need a delete operator to dertermine how long a particle life lasts, then animate the scale operator from frame 0 to what your particle life is (in my case 50) and set the scale operatorīs "Animation Offest Keying" to "Sync by Particle Age".

hope that helps,


08 August 2008, 03:10 PM
Psycho, that works great to scale everything down globally across the whole pflow system, but I only want to scale the particles after a certain age. to use your example, is there a way to only scale the particles after they hit the 50 frame age? Before frame 50, they would all be the same size.

The effect I'm trying to get is a tapered look at the end, but not along the whole length of particles.

Here's an image to show the tapering effect I want to achieve. I got this to work by linking about 15 events together with age tests, each one with a decreasing scale factor. The only problem with that method is it takes about 18 minutes per frame to render. That render was cropped, so it is just showing the end section of the thick line that continues on.

08 August 2008, 03:46 PM
Yep that's easy enough too - what you'll need to do is use an age test at the end of your first event set to 50 in this case so that after 50 frames, all the particles go to the next event. In the second event put your animated scale except this time set it to event duration - this will sync the scale animation to start as the particles go into this new event. Put your delete in here and add up the number of frames from your first event (50) and the number of frames that the particles scale down over. So if you had the scale running over 30 frames you could set the delete op to 80.

08 August 2008, 03:54 PM
Set you particle delete age to a value greater than 50 and animate the scale value from frame 50 (frame will correspond to the particle age) to whatever.


08 August 2008, 04:24 PM
Ok Thanks guys, I got it working. Really appreciate all the help.

Some more notes on what else I had to do - Scale type has to be set on Relative First. Animation Offset Keying had to be set to Event Duration as pointed out by joconnell.

One other thing is that the animation keys for the scale, (value of 100 to 0) had to start on frame 1. No matter what frame the age test transitions into the 2nd event, those frames have to start on frame 1. Because when you set the scale settings to Event duration, frame 1 is frame 1 of the new event. I think that's how it looks at, not sure, but it worked for me anyway.

Thanks again for the help!

08 August 2008, 04:37 PM
Theta you're bang on with your thinking - otherwise pflow wouldn't have a clue how to sync anything with particles being born at different times - you always animate things from frame 0 onwards unless you're setting your animation to absolute where it'll use whatever the scale value at that frame is.

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08 August 2008, 04:37 PM
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