Quote:
"Irradiance normal mapping is a method to combine two popular techniques, light mapping and normal mapping, and is used in games such as Half-Life 2 or Halo 3. This combination allows using low-resolution light caching on surfaces with only a few coefficients which are evaluated by normal maps to render spatial high-frequency changes in the lighting."
Now that sounds like it might work in combination with the virtual texturing surface caching idea!
Not sure about it's performance though, which is rather crucial.
You can find the paper here.