Nodraw

I won't get to use the new editor for a little while but I have been reading around and apparently something called nodraw happens to be an apportant part of making maps for CS:S. Can someone who is using the editor right now tell me what this nodraw does?

nodraw is the equivalent of caulk in Q3/D3 and null added to the MHLT tools in HL. Just deletes that face/those faces from the renderer. Useful behind models, backfaces of brush entities, etc. etc. Also required behind the new func_detail entity to seal the world.

I saw in a pic of DOD source that they were using a brush with the nodraw texture on it to do a lighting trick.

Func_detail... as a replacement for func_wall wich we always used to make the VIS process a bit easier?

Correct - func_detail is a new entity that has the inherent properties
of a brush entity (in that it doesn't cause face splitting when
touching a world brush, doesn't block visibility, etc...), but it has
none of the performance overheads associated with entity brushes as it
has no extra data like func_walls do.