Due to the very similar design and syntax, how hard would it be to write a convertor or parser that would convert between the three high-level shading languages: HLSL, Cg, and HLSL?
If I remember correctly, HLSL and Cg were designed to be interchangeable. Having not used both, I'm not sure how much different Cg/HLSL are from GLSL though. If it's a matter of syntax, the conversion would be relatively easy I'd expect. However, if the languages were divergant on a deeper level, it could be harder because you'd have to actually change what code does (imagine converting between C and python, or lisp and basic).