ACE Engine will now read textures between TX_START and TX_END lumps. There can by any amount of these sections.
Unlike in doom2.exe, textures can have any power-of-two height. Original game limited texture height to exactly 128px.
Further, medusa-bug was fixed. You can use multipatch textures on middle walls.
Original power-of-two width limitation is still present.
If you don't care about compatibility with other source ports, and don't intend to use original texture definition system, you can just enable doomtex.workaround config option.
This option will invalidate all conflicting lumps that exploit uses, thus original doom2.wad lumps will be found instead.
Alternatively, you can rename PNAMES, TEXTURE1 and TEXTURE2 using DEHACKED. This should allow you to make mod compatible with other source ports.
Except, this does not work in GZDoom!
Sometimes, for 3D floors, it is good to have transparent texture, like metal grid. Doom flat system does not support transparency for flats. Thus a new workaround was made.
Any textures with resolution of 64x64 can be used as flats. Though, this doubles the memory requirements as texture for wall and flat has to be stored separately.
Also note that textures on flats can't be animated using animdefs.