best practices - overlapping brushes?

(fraco) #1

I’ve seen ppl stating that overlapping brushwork was evil. I’ve seen ppl systematically overlap brushes to save tris (instead of goddamn mitering those edges).

I personally am using some overlapping brushes in the map I am currently building, so I am looking for a definate word on this (before i get to the point where i have to redo half my map).

Can I overlap brushes or not?

I do know about the z-fighting issues if two textured faces overlap.

What is the bad effect of overlapping brushes?

fraco

-> overlap does mean “occupy the same space” in english?

(damocles) #2

It’s a grey area with different rukes for different situations.

If we’re talking about overlapping where two walls meet - that’s a definite no-no.

If we’re talking about having a wall overlapping a little way into the terrain, that’s not so bad. You’ll get some overdraw and maybe a bit of z-fighting in some cases, but generally you can get away with it as long as you understand what causes the z-fighting and avoid it.

Overlapping water and fog brushes as almost completely unavoidable and is usually fine, as long as you don’t overlap two water brushes togetehr (or two fogs). Only overlap against regular brushes.

And I’m not sure what you mean when you say

I’ve seen ppl systematically overlap brushes to save tris (instead of goddamn mitering those edges).

Mitering is the way to save tris, not overlapping.

(fraco) #3

hi,

thnx for the reply. I was thinking of q’s sample map thread over at quake3world:

http://www.quake3world.com/ubb/Forum6/HTML/020488.html?

if you look at his example on how he avoids overdraw, you encounter this pic:

see how he overlaps those brushes instead of some funky form of mitering?

Any more thoughts on this? What effect does this have on the bsp? Is it really bad?

I myself use it because the inside of a building has been cut up in a lot of brushes, the outside I didn’t want to have all those separate surfaces, they weren’t needed. I overlapped the brushes that form the inside wall (a lot of them) with the brush that forms the outside wall, textured only the appropriate sides and used caulk on the other to avoid z-fighting/overdraw.

The reason I don’t just put the walls back to back is because all my doorways would otherwise be made up of two surfaces (half of the side of the doorway would be the face of the “inside walls”, half of it would be the face of the “outside walls”.

I know, this text makes perfect sense to me, but there is no way anyone else is going to understand that. I’ll try to post some screenshots later.

fraco

(damocles) #4

As I said, it’s different rules for different situations. Experience and common sense will tell you when and when not to overlap or mitre brushes. In the pic above, he can use non-mitred brushes because it is an interior section and the outsides of those brushes can’t be seen.

And the overlapping he is doing there is overlapping caulk. Caulk never gets drawn or even compiled and so can be safely overlapped onto other brushes. If you had caulk filktered out in that picture you would see that his regular brushes do not overlap, they simply touch.

(fraco) #5

ok,

thnx again for the reply.

Is it a safe conclusion to say that overlapping brushes don’t harm, except for overdraw and z-fighting, if not thaught-out well? I am aware of those issues, but I was worrying about e.g. splitting of the bsp (with two overlapping structural brushes)?

thnx

fraco

(damocles) #6

Techinally two overlapping structural brishes won’t break anything, the worst it might do is cauase extra vis portals wjhere you don’t need them.

However, I would highly recommend against overlapping structural brushes. In reality, what you should be doing is making the caulk brushes structural, and then overlapping them with detail brushes. So in other words, your walls with textures and other crap on them are detail and then underneath them there are solid caulk brushes minus the detail and extra rubbish. This simplifies the BSP/VIS process because only the structural caulk brushes have to be taken into account and all those hundreds of detail brushes won’t chop the portals into a mess.