Growing particles over time

[kruger35]

I'm creating a smoke trail behind a jet, and I want to feed the age of the particle into the scale of my copied spheres, as well as into the color of each sphere. How can I do this?

[diamonddave]

If you're using POPs (the particle editor), then you can put down a Property POP and in the Particle Scale field, write an expression which indexes $AGE (or $LIFE). Another way would be to use a Color POP and put $LIFE into the index and think of the ramp representing size over age, and then in a Property POP, swap a color channel (e.g red - $CR) into the particle scale.

[kruger35]

Thanks for the reply! I ended up doing it in my Copy Sop. In the uniform scale I put this expression (I don't have it in front of me but something like this);
spline($AGE,.3,1)*10
I'd like to be able to use $AGE to reference a keyframed channel so I can more explicitly control the scaling over the particle's life; how would you recommend doing this? I'm not too familiar with Chops, but I'd guess maybe that's the answer...