so i purchased the intro to zbrush from the gnomon workshop, and in chapter 24 he is painting an object that is not posted symmetrically, but he is painting both arms at the same time, and then says “as you can see, i am using topological symmetry, which isn’t what we want, but we’ll get into that later” and then clicks some keyboard short-cut and i have no clue what he did… and i have watched every chapter and have no idea how to turn this feature on.
please help.
thank you in advance,
Andy
transform>use poseable symmetry
your cursor will be green instead of red when you have this active.
Always active it at your highest subD level.
If you create another subD level (a higher one than before) you’ll need to go to the highest level again and active it again.
Hope that helps.
that’s kinda what i assumed… when i do that tho, zbrush just seems to lock up for 30 seconds to a minute, and the when it responds again, it is just the normal symmetry, not topological… 
is the object symmetrical? I don’t mean “no, because it’s posed” I mean, if it were in a T pose, is it symmetrical?
Also…the “lock up” is Zbrush thinking about where the central line is and how to set up the poseable sym line.
I’m not sure off hand, but I think the model had to be symmetrical to start with otherwise poseable symmetry doesn’t work.
this is the character… i haven’t posed her yet cuz i am scared to lose the symmetry… if you see the 2 green dots… that’s where zbrush thinks symmetry is, but if i use normal active symmetry and not posable it’s fine 
Try Smart Resym, then see if your symmetry line works better. You may have just inadvertently lost symmetry at some point.