Hey, I'm gonna try to reply to all questions shortly. I'm just terribly busy with university lately.
I'm not an expert yet, but I will try to answer.
1: Most polyhedra will have different textures on different faces, so why not start with all caulk and apply textures to individual faces only? This is not much more work, but it will reduce your future problems, because:
Originally Posted by tenthu
2: In SOME cases, there are performance issues (for an unknown reason, q3map2 doesn't remove invisible faces from `detail` brushes, so they will be drawn if they have a drawable shader) — so if you have unnecessary textures, you can get massive hassle when you decide to make these brushes `detail`.
Also, you may get z-fighting issues and unnecessary drawable triangles when a patch is placed over a brush with drawable face (because patches don't block visibility, everything beneath them is drawn)
3: caulk faces have an advantage — you can safely overlap them with other (visible & drawable) faces, if there is no nicer way to lay out things... but overlapping 2 visible drawable faces will introduce z-fighting (which totally sucks!) and maybe also something even worse.
Ok, here is a few facts.
1. there is two kinds of brushes: structual and detail
2. detail brushes don't affect visibility calculations (what is rendered on your map), structual brushes do
3. invisible surfaces of structual brushes facing the void don't get rendered by default
4. invisible surfaces of detail brushes always get rendered
5. thus detail brushes need to be caulked and then textured as needed, though it is easier to get used to just using caulk on everything
6. Why do I need to use detail brushes if they cause me more work? Simply because using them is important for your map's performance.
Structual brushes create portals along their boundaries. Visibility is calculated by "portal visbility" which effectively means nothing but IF portal A of brush 1 can see Portal B of brush 2, render brush 2 and vice versa.
For a more indepth view on this, check out this thread about hint surfaces (hint surface = portal): http://www.quake3world.com/forum/viewtopic.php?t=3620
This is pretty complicated when you are new to mapping and you do not have to fully understand it to make a working map. Just get used to using caulk on your brushes' invisible surfaces and convert as many brushes to detail as possible while keeping the brushes that structure your map structual (i.e. the outer walls of your rooms, hallways etc.). Don't drag a huge structual box around your map and convert everything inside to detail as that will make the compiler think that your map is just one large room.
If you got further questions feel free to ask.