Some of you may know that I’m a bit of an advocate for the use of portals in creating dynamic virtual environments. I’ve published a few papers, and generally think that they are pretty cool. I’ve also recently written a few new algorithms for portal rendering (not yet published). Unfortunately, the use of dynamic, place-anywhere portals has been fairly limited in commercial products.
Static portals are fairly common in game engines. They are usually manually placed in a level to optimise rendering (just making the game run faster), but they have also been used for reflective surfaces and transportation devices (sometimes you can see through them and sometimes you can’t). Prey (a game in development for a very long time) is the most recent game to include portals as a key gameplay feature (to create interesting, physically impossible spaces).
Here are a few screengrabs:
It’s nice to see a game actually using dynamic portals in an interesting way. The promise has been there for a while, but this seems to be one of the only games to use it. From a technical perspective, there have been barriers to adoption of dynamic portals. Chiefly, it can make rendering much more difficult if using a conventional engine. I read on the 3D Realms forums that Prey’s portals “black out” with distance to limit draw requirements.
From the demonstration video, it seems that Valve is getting around potential technical problems by ensuring that their portals are still somewhat restricted (there’s only two, they only appear on walls, and are always planar and elliptical). I’m still looking forward to the appearance of even less constrained (say, 3D animated) portals in commercial games. Something like those demonstrated in these old videos I made.
Update: AusGamers have the video for download in a zip file. Recommended