   What kind of projection is this? (Sonic X-Treme)
  I've stumbled upon some videos (e.g. ">Crystal Frost, ">Death Egg) of the unreleased Sonic X-Treme on youtube. The unusual projection sparked my curiosity. At first glance it looks like they used regular perspective projection and turned the fov way up, but on a second look it becomes clear thats not it. E.g. straight lines are projected as curves. This can be observed in some raytracing demos, such as ">this. I'm not sure if that is the same projection as in Sonic X-Treme, though...   
Fisheye is the name of that effect.   ;  Ah, yes, that sounds about right. I've programmed a fisheye zoom as a posteffect, but it didn't occur to me to use it in this way.   