Thief uses a new engine developed by Looking Glass, and while it is impressive in certain ways, it s hard to say that it s on the same grounds as Lithtech, Quake II, or Unreal. Things are a bit boxy, and it s easy to get a distorted sense of height in the game, even from objects that are obviously small. And the water effect, unless it's set to a deep rich blue, is worse than even GLQuake's. The stream on the training level looks so bad I didn't realize it was water until the game told me I could practice swimming in it. On the other hand, there are quite a few things done well.
Colored lighting is used subtly but well.
Torches flicker, lanterns cast light around their iron bars rather than through them, and the splash of the fire and water arrows is especially nice. Humans move exactly the way they should, be they zombie, drunk guard, or fierce Hamerite zealot. You can really get a sense of personality by stealthily watching a person in the game, and a lot of that comes from the gestures and body language painstakingly added to the game. The controls are similar, but its more like Trespasser done right than Half-life. Its all about timing, all about planning and striking when the time is right.