directx, the way i understand it allows direct access to the video card(for hardware accelleration). linux(actually X window) supports hardware rendering through a DRI(direct rendering interface etc.) thingy that you need to compile for your video card for it to work. (i guess thats the equivelent of directX, - but i hear that direct x isnt exactly "direct"
)its a shame though... snazzy hardware acceleration under x windows only works with a dozen or so cards