This image right here has the caption "This many people never appear onscreen in the final". In fact, that amount of people never occurred onscreen at all ingame. It's a prerendered image. You can tell by looking at the shadows - level objects are casting shadows (not possible in the adventure engine) and the people aren't casting the usual plane-mapped circle shadow, they're casting polygon shadows (also not capable in the adventure engine). The smooth polygon shading also doesn't match the adventure engine's. This screenshot only shows me one thing, and that is that at one point during development, level models faded into existence once they reached the beginning of the draw distance zone - look at the long road path stemming from the side of the building in the upper left hand corner. Notice you can see the fencing for the sides of the path, but the actual road surface has faded out and then back in. My only reasoning for this feature being removed (as it visually is much more subtle and pleasing) is that it must have been too processor intensive to maintain a steady framerate. Not that sonic adventure had a a steady framerate to begin with.