[lsh]

Duke Nukem 3D/Shadow Warrior and the Build engine also achieved a number of their effects and mechanisms similar to the video. In fact, the very first level in the first episode of Duke Nukem 3D where you're on a rooftop, pick up the pistol, shoot the fan and drop down the shaft is a perfect example - that rooftop and the street level you drop into are connected seamlessly by a short tunnel that transports you. Water surfaces were also used in this effect and the 'underwater' parts were often entirely other parts of the map.

I always thought of them of as pre 'true' 3D engine hacks, but it was so cool to see them again in that video. Cooler still that it's essentially the same trick being used in Portal and I never tweaked to it