Created attachment 87786 [details]
Screenshot of the fountain on a newly started game

On a HD4850, DOTA2 in-game background and some other objects aren't being
rendered. Attached screenshot shows the problem well.

DOTA2 graphics settings are at the lowest (didn't help). This is using git
mesa3d on a current (~amd64) Gentoo, built both with and without LLVM shader
compiler backend. Kernel is 3.12-rc5.

It has, to my knowledge, never worked... I kept trying it once in a while for
half a year.

Since nobody else has complained yet, I suspect it's a problem that affects
only the HD4xxx line of cards.