I am trying to figure out how to use a smaller program for old CNC machines to do 3d profiling with a parallel toolpath. It's perhaps a bit hard to explain, but it boils down to an algorithm or some way to find two stepovers that don't intersect (or at least not often).

What is the appropriate "math stuff" to use to solve this problem?

with a 15 thou (0.015") stepover the passes will be:
0.015", 0.030", 0.045", ...

with a 3 thou stepover, the passes will be:
0.003", 0.006", 0.009", ...

when the two "sets" intersect with the same value it is wasted time.