i came accross this when looking for some shaders to make realsitic reflective water and this shader comand looked like it could be pretty usefuly but have some vaigue memory of a thread ages ago of fog trying to get fog within a water brush
q3map_backshader <shadername>
This allows a brush to use a different shader when you are inside it looking out. By way of example, this would allow a water brush (or other) surfaces to have a different sort order (see sort above) or appearance when seen from the inside.
(again no computer to terst this on but)
would it be posible to make fog that only shows when inside the water brush so the upper water surface can have rising and lowering vertices to make less calm water with fog
can also be used to stop the mirror working when inside water