I have read a bunch of video card reviews that talked about how TnL GPUs are not important yet because most games do not use them. This got me thinking about how it is enabled. Please correct me if I am wrong here.
OpenGL TnL. This is all done in the video card drivers. Code written last year will be TnL accelerated when run on a system with a TnL card. There is nothing special needing to be done to get the benifits.
Direct3D TnL. DX7 came with a TnL interface. If this interface is not requested, you don’t get TnL acceleration. Since this interface was not around before Dx7, everything written before that ( <= Dx6 ) is never going to request it.
If this is true, it is possible to write a D3D program now that doesn’t use TnL accel. but OpenGL has to use it (if it is avaiable). This leads to another question, why would you ever NOT want to use TnL acceleration?