Simple questions: If you have a large brush that extends across much of a level, should one split it into smaller segments? (there are some game engines that choke on large map entities)

if you want to add some its easier with small brushes but large brushes are ok

You should split them up a little, as a brush face is either rendered completely or not at all. However, the gain you get from that is quite small. On capturecity, this optimization (dividing the big street layer into smaller parts) brought just about 1% of frame rate, nothing big (the big improvement, however, was achieved using hint brushes and a better blocksize). Speaking of hint brushes... look at capturecity - I built some hint brush pyramids on the towers so the items can't be seen from below when one is in the half of the map that can't see them. The other hint brushes on it were quite straightforward.

Theres a pile of reason to devide big brushes, and only one reason not to.. lazyness

#1 preformance. Like divVerent says, a face is randerd or not, never halfway. On a simple texture/small number/samll area youmay not notice it to mutch, but its still "the way to do it" On big and comples textures (think translucent, glowmaps, animaps etc) it can gain you extreamly mutch speed to split the brush.

#2 the biggest possible space on the lightmaps you get from q3map2 in 128x128 (the size of one lightmap) pixles. a brushs sized 1028x1024+ qu's will never ever have a sharp shadow on it (unless you use a shader to tell q3map2 to subdevide it). A big brush sharing two rooms can lead to light/shadow leaking between thise sizne there not tnougth room fpr the presition needed to not make this happen.

#3 Texture alignment and ease of edit. Always build geometry in logical blocks unless you have a calr reson not to (like hints or hidden visblckers). Its mutch easier to align a texture inside just one room then it is to align one to fit nicely over 3. It will also be mutch easier to see each zome in the 2dview of your edtor if ya keep brushes beloging to one room/section.

Clipping, facedragging and edge (not vertices!) manipulation are your friends, use them. A nice way to make the outer edge of a room look good and keeping from overlapping unnessesary is to cur the edges of your walls in 45dgr and match em up. this means no unnessesary textured area and a smootn outer wall. hmm better do this as a visual tutorial. stay tuned.

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Here it is, a quicky tuorial - http://zdev.dvrdns.org/tutorials/tut1/tut1.html
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