Getting the "Max_Map_Brushsides" error when compiling my map. How to fix? [anon.]
You have a brush that is too complex. [anon.]
You have a single brush volume with too many visible brush sides (unlikely, usually results in a different error), or the level in total has too many (most likely). As simple as that. Possible solution, slice up brushes which have sides not visible to use fewer sides. [Kat]
[Addendum] The map in this instance has too many visible sides - each brush as a cuboid convex volume typically has six sides by default when drawn, if all are textured with 'gothic_wall' it means all six are considered and potentially visible to the compiler, too many brushes like this and the "Max_Map_Brushsides" error may occur (because the TOTAL AMOUNT of sides visible in the level exceed the limit, c. 32k). To avoid this, texture unseen/unused surfaces with "caulk" (or 'nodraw' or other clipBrush volume where necessary), and combine brush volumes together to minimise the number of brush sides visible. For complex structures, e.g. three-point clipped rocks for example, rather than leaving them whole (as created/clipped), clip and remove unwanted/unused/non-visible surfaces or sections - Max_Map_Brushsides tends to happen in complex detailed levels or maps with a lot of clipped abstract structures [kat].