An entity brush overlapping a world brush is not neccessarily a problem. Ive never had a problem with it anyway...

Ideally, no brushes should intersect. However, if it is unavoidable, its a good idea to make one of those brushes a func_wall.

i just have to ask, if one knows its overlapping, why not fix it?

i mean really, all unknown overlaps are unavoidable, even i find a few i have made accidentally, usually after i have released, so its too late to fix it.

but really, isn't this a redundant or rhetorical question? since knowing its overlapped, shouldn't you fix it in favor of either proper mapping technique, or at the very least to prevent the outside chance it could cause issues?

personally, the perfectionist in me, won't let me knowingly leave a defect in my map.

sadly, few others share my passion.

i say, if you know its overlapped, fix it.

as to the question at hand, it is my understanding, that any unseen overlaps are clipped out during compiling.

There are scenarios where letting brushes overlap can save a lot of hassle and even faces. For example, imagine you have some really simplistic triangle terrain, and put a 10-sided cylindrical object sort of "dug in" to the ground. Now if the terrain is really simple the entire cylindrical object sits inside the bounds of only one triangle. to make the objects NOT overalap would require you to either...

1. Clip the base of the cylinder to meet the gradient of the terrain. In the case of the terrain sloping over two axis, could be tricky, and if the gradient doesn't line up exactly you could get some dodgy light artifacts around the base OR satchels / snarks could fit under the object.

2. Manipulate the terrain to meet all 10 sides of the object. Doing this would mean your single triangle that previously made up that part of terrain would be split into around 10 triangles, wasting loads of faces.

If however, you just let the object overlap the terrain and turn it into a func_wall, then none of the disadvantages of the two above solutions will rear their ugly heads

PS. Should I detail this further in a tutorial?

Actualy, I am in pretty much exatcly the situation which ReNo describes. in my dod map I am trying to model debries with triangle terrain, but I would like to imbed some bricks and bits concrete to increase realism, but as reno suggests, it would require some pretty laborious work and many extra faces to fit them into the terrain neatly.

I guess this is the question I should have asked to begin with. I'm still not sure though, because in the case of making debries, I'm going to have to put probably 30-40 of these in the map, which makes me very nervous. I normaly don't overlap anything; not even water.

Despite said otherwise, overlapping world brushes generally won't do anything. You won't ever see thos intersecting brushes, so it effects nothing.

So long as the textures don't double over, go ahead and overlap. Th main game did that all the time, even in the dam level.

I overlap func_walls into world brushes all the time. It makes certain things a lot simpler and never hurts anything unless the edge of a func_wall gets outside and 'leaks'. I usually try to avoid world brushes overlapping; usually you can easily make one of them a func_wall anyway, so...

little trick if you don't know it. know how sometimes a sign on a wall (thin brush against another brush) will flicker in the distance? it's a rendering bug with the z-buffer i think.. anyway, if you make that sign etc. a func_wall, then extend it back into the brush behind it a bit, it will fix that bug. very useful sometimes. (making it a func_wall just avoids face-splitting etc.)