I have a situation where I need a particle emitter to emit custom particles from left to right but when the particles reach a certain point on the screen, they need to slow down as though they are passing through a jello block. After they leave the jello they need to speed back up to their normal speed.
Is it possible to use expressions on a per particle basis rather than on the emitter, allowing me to change particle velocity as individual particles reach a range of positions? Or can anyone think of another way to accomplish this same effect?
I have access to Particular as well as the native AE tools.
I don't know of a way to control the speed of the particles individually, but one thing you might try is to pre-compose the particle animation and then use time remapping on the pre-comp to control the speed of the particles.
This would work except not all of the particles will be entering and leaving the jello at the same time. If I use time remapping, won't all of them slow down or speed up regardless of where the are in relation to the jello?
Yes, good point. Could you use a separate layer of particles that are moving slowly just for the Jell-O part of the scene? Maybe use a mask to isolate the portion of the screen where the Jell-O is? It wouldn't match up perfectly of course, and it may also look weird that you've got particles moving very quickly going into the Jell-O and then suddenly moving slow through the Jell-O. I think they would probably need to slow down as they are entering the Jell-O for it to look realistic, but I'm not quite sure how to do that.
This ZIP package includes an AEP (2 versions in AE CS6 and AE CC). The AEP uses Particle Playground to create particles that are shot off a canon (emitter). The particles then travel at variable speeds. The speed is controlled in a precomp using a grayscale image.
White areas denote fast/normal speeds. Darker areas denote slower speeds. As a particle travels across different luminance areas, its speed varies accordingly.