Radeon HD tesselation usable with Renegade game engine.
http://developer.amd.com/gpu/radeon/Tessellation/Pages/default.aspx#documentation
Both documentation and library is what you need.
It looks relatively easy to implement, since there is a use of d3d8.dll and d3d9 shaders there's no big problem to compile it with custom AMD library addressing tesselation engine in HD2/3/4/5k series of cards - with Directx9 (so no need for Vista and DX11). C&C Renegade used ATI Truform tesselation engine withRadeon 8500 and 9700 cards with quite nice visual improvement. Truform was abandoned some time ago, but faster and better tesselation engine was developed by AMD. Implementation of that could improve all those blocky models without major performance hit.