You'll need the precomputed Beckmann distribution in a texture: http://developer.nvidia.com/node/171
There should be still some performance margin left, I tried to tune it to keep 60 fps on my notebook.
Visual difference is quite subtle - skin feels more "silky" and ears are more shiny.
No noticeable degradation of performance.
There should be still some performance margin left, I tried to tune it to keep 60 fps on my notebook.