HardOCP analyzed the performance and image quality of various AMD and NVIDIA graphics cards in The Witcher:
The Witcher uses BioWare's Aurora 2007 Engine, which also powered Obsidian's Neverwinter Nights 2. An earlier version of the same engine was the foundation of Neverwinter Nights 1, which was BioWare's own production. The updated version includes pixel shading and hardware Transform and Lighting. For more detailed information about the Aurora engine, please visit BioWare's Neverwinter Nights development site. The key thing to be aware of regarding Aurora is that it is an old engine, and has been updated over the years. That kind of evolutionary development cycle tends to result in stable, efficient games, though that is not always universally the case. Furthermore, it is almost certain that CD Projekt Red further adapted the game engine to their own needs.