3D Bridges

[DSC]

How do they exactly work? I have seen quite a lot of them by now, but I still ain't sure about how to build them. They seem to be made with some kind of 2D texture, so I guess it is something related to that?

[Marlamir]

Here if your target is zdoom based source-ports:

 

and if for boom i believe this should help.

 

[galileo31dos01]

... and if in vanilla, then I recommend watching this.

 

Typically the texture used is STEPTOP as a mid-texture, though you can also make completely invisible bridges like in Plutonia map 03. The trick is in the self-referencing sector(s) which you'll use to step on and cross the bridge. The tutorial I linked to explains how to make them. Then for examples of multiple fancy bridges it is worth checking Kama Sutra and/or Requiem. 

 

Notice that drawing 3d bridges in vanilla is outdated and bound to break if not taken with caution, though no less of a cool trick if that's what you're looking for. In Boom you'd avoid the trouble as there's already an action to create fake floors and walls. Up to you.