Debian does not include any proprietary drivers with its install. You will need to download the appropriate driver for whatever ATI card you have. My knowledge is more specific to SuSE, so I can not advise you how to install it "The Debian Way" once you have it. I am sure that where ever you get the driver will have installation instructions.
FYI: VESA is the generic driver so hardware acceleration/3D are not controlled.
Again you need the proper driver in order to get 3D working.
PS: You might get more information specific to your post if you post it under the Debian Forum.