Portals are not the same as just walking through a teleporter, or even the concept of being able to look through one and seeing the other side. In Prey, everything is a portal. In the demonstration, we were shown our hero Talon Brave, standing still, looking totally kickass with his gi-normous gun. Nicely rendered yadda-yadda. Then the camera pulled back.
Prey uses portals literally everywhere .
At one point, Paul showed us a standard level, and he ran through it. As was every window. And any place there was water. Hell, in one part, the floor , a reflective surface, was a portal. And damn , are these some detailed levels.