I spent the last few days being baffled by an area which would show up in r_showtris, despite being around multiple 90 degree structural corners :banghead: . While trying various things, I found that this only happend with -meta compiles. Portal viewer showed, that the areas in question shouldn’t be able to see each other, and bobtoolz viz viewer seemed to agree.
Finally, I realized that the bits showing up were were connected to, and shared the same texture with, parts that could be seen. If I understand right, that means these are candidates to be merged together into one metasurface (?) and if one bit of the metasurface is visible, the whole thing gets rendered (?).
Recalling something in the changelog about -meta not merging func_groups, I grouped some of the bits together, and it indeed seems to have solved the problem.
I guess the moral of the story is not to make big bits that are all one boring texture. Or maybe I misunderstood the whole thing, in which case clarification would be nice 
q3map 2.4.5, BTW.
Oh, other than that, it is compiling my ut2k3 map very nicely :poke: