Good: You can make a place feel consistent rather easily, and you only need to do about 1/2 the work.

Bad: It can get rather stale with the map or each room being symmetrical. It can stifle creativity - my levels tend to become symmetrical without me trying. It's just easier to rely on making something symmetrical than to put in thought to an asymmetric layout. 

I'm not talking about making _every_ room symmetrical. I think symmetry in places makes level more solid. 

i tend to make ending arenas symmetrical. they are easier to account for combat especially if you're doing a boss as well as making it easier to build because you're only doing half the work.
when you say it that way, it sounds like you're just trying to save time, but in reality, it lets you put in twice the work on one half of the area. 

Saving time on brushwork lets you spend more on game play - same for the player when they're there.

Most arenas are the same, since they're supposed to be intense battles.

I try to avoid symmetry in SP, even if two areas are roughly the same I'll break the floor on one or give it slightly different detailing. 

Symmetry is the easy way (cheap even). It's okay for certain areas, but shouldn't prevail in every single room. Symmetrical monster placement is another thing - best to avoid making excessive use of it, it can make gameplay boring. 

I think it's appropriate for areas that would be symmetrical in RL, most of the church-type buildings in SoE were semi-symmetrical, or the church-type start of nsoe5. nsoe6 I tried to break up the symmetry some, but it was a bonus map so I wasn't as worried about having it symmetrical, though I do agree that this can take away from the gameplay, especially the sense of exploration. making one side ruined might help. 

symmetry may be used to create a surreal atmosphere of an unnatural place built by some higher force. For example in the map I'm working at there is an area that has both vertical and horisontal symmetry which is used to create a specific highlight of that area. 

I always used symmetry to make architecture to be more believable. If you look at any house in real world is's symmetric, hence if you have geometry in the game built on these principles, player won't be confused. But I always break symmetry a bit here and there, i call it "asymmetric symmetry" if you know what I mean. Because if you make some random architecture out of your brains, usually it looks like heaps of brushes rather than logical structure. 

I've never seen a symmetric house in RL, but Elements was a very interesting reminder of using basic design elements well, as opposed to say giant setpieces, and using them inefficiently (as I often do). SolarFall seemed to do the same thing, but at that point (when Tyrann was doing Moonlit and Elek was doing Golgotha) it was also a good point. 

there's also how close you want to examine for symmetry... like right down to the hallway level, for example. 

making entire level symmetric is wrong, it works better just for one hall/room. 

 

far from it 

 

IT basically adhered to what he said in his post:

I always used symmetry to make architecture to be more believable.

In Vondurs last map the halls had a degree of symetry (a large degree) in the architecture - i.e. an arch is symetrical. Especially in modern/gothic architecture. But the layout of the map wasn't symmetrical. 

that's the point of my so called asymmetric symmetry. 

Symmetry is cool, but needs to be broken otherwise it becomes sterile. Easy to do in a ruined dungeon - just ruin one side a bit more, put a different puzzle or obstacle on the other... in this way, symmetry can be nice. Like flawed beauty. Variations on a theme are an art, same for variations on symmetry.

It has its place. 

I think that it really depends on the setting of the level as to whether symmetry works or not. Organic environments are rarely symmetrical while man made environments that don't have any organic obstacles tend to be quite symmetrical in general.

In Quake (in fact with most FPS's in general) the environment is primarily man made and (to some extent) industrial so most levels are set up to deal with organic obstacles like cliffs and water or similar environments which help it become more varied in its symmetry with a believable reason for the loss of symmetry.

The other main reason for loss of symmetry is damaged structures (such as ruins) which also lends to believable man made environments that aren't dull or repetitive.

This is also why cities or towns that have to build around the natural environment are almost always more dramatic and visually appealing than cities built out in the middle of a plain somewhere. 

is that ever true. prairie cities are a bunch of flat boring grids, coastal/mountain cities always look more interesting/have cooler layouts. 

This is also why cities or towns that have to build around the natural environment are almost always more dramatic and visually appealing than cities built out in the middle of a plain somewhere.

yeah, i love seeing a city/town built around some wild natural feature.