I want to have particles travel down a spline and get narrower as they encounter bottlenecks. Picture a tube which narrows. I want the particles to flow with and to narrow with the tube. It’s not the individual particle size I want to change, but the width of the stream. I started with position by icon but can’t figure out how to vary their width except by scaling the icon. That changes their width from the start, not along the path at a desired point.

Set the Icon Animation to sync by Particle Age and animate the icon when the first particles reach the bottleneck area of the tube.

Or if you have Max 2010 or higher, use a piece of geometry for the particles to slide on the surface of and a lock/bond test. Change it to Lock to Surface, check Restrict to Surface and set the position and rotation lock/bond % to 0.

3ds Max 2009 SP1, 2010 SP1
Maya 2012
Windows 7 Professional 64-bit
Dual Intel Xeon E5520, 6 GB Ram
NVIDIA GeForce GTX 460 OC

Thanks so much for the help. I’ll try this. I assume it will work. This stuff is complicated, with a lot of different ways to configure things. I appreciate the help.

I tried changing the Speed by Icon Icon Animation parameter to sync to Particle Age. I get the same result. When I animate the emitter size, the width of the particle stream changes, but it does so from the emitter outward. I want the stream to narrow at the bottleneck (and later enlarge again if necessary), not at the emitter.

I did come up with a sort of solution, but I’d like to make this work by animating the emitter if possible. The solution was to shoot the particles into a tube of varying width and make the tube a deflector with a UDeflector. The particles bounce off the walls and narrow down. This could work, but I’d like to be able to animate the width of the stream from the emitter if that’s possible.

Works fine here.

3ds Max 2009 SP1, 2010 SP1
Maya 2012
Windows 7 Professional 64-bit
Dual Intel Xeon E5520, 6 GB Ram
NVIDIA GeForce GTX 460 OC

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