by daemonicky » Sun Jun 26, 2011 2:37 pm
a) Dot product their directions (or velocities). Look for sign of result.
b) compare if distance between them gets larger
c) do b but use some statistics, epsilons, or cummulative change (sum of all changes in few miliseconds to approximate if he is moving in not being on the same spot) ...
frag.machine good idea tracking the health
Think, touch, movetype, solid, traceline ...