Change scale starting after particles move

[adrencg 0]

I have an object covered with particles that have their speed set to 0. I'm using a spherical falloff object to "lift off" the particles with xp turbulence. How can I use xpscale (with radius change) to scale to zero smoothly after they start moving? I tried using questions and answers to use the scale once a distance traveled has been reached, but there was just a popping of the particle over 1 frame, not a smooth transition over time.

Edited Wednesday at 01:08 AM by adrencg

[adrencg 0]

I almost have it figured out, but some of the particles are popping instead of gradually changing size. I attached a scene if anyone has time to take a look to see what I'm doing wrong.

turbSphere.c4d