Hitting a bug ?
Be sure to test on this version of Mesa first: https://github.com/iXit/Mesa-3D/
Here is the list of known bugs:
Emulated fog behaviour not implemented (old games only)
Fixed function pipeline has a few bugs
Stateblocks have some bugs (CIV IV: black textures, etc)
Minor graphical error(road texture in payday2. Red shadows on Unreal Engine games)
Bad window messages behavior (causes some games to not start)
Red shadows on Unreal Engine Games for radeon. We have no way to solve this bug (we'll need help from AMD).
Wish to help debug ? Come on our irc channel
Or report here: https://github.com/iXit/Mesa-3D/issues?