I am glad you all like this, in my opinion it shows that the team at Point of View was much more capable than they have been credited, at least by the Sonic X-treme community, and credit is deserved.
The code the way I found it is essentially a setup of POV's Saturn game engine, with some specific additional code dedicated to implement the Sonic gameplay.
The engine itself provides 3D graphics, clipping, sprites, animation, has a full cooperative multitasking model (very good, especially for the time).
The level converter was written ad-hoc to convert the DEF + PCX data structures that STI's engine works with in a much more streamlined binary format, which includes collision data, and groups graphics entities in batches, so that the camera transformation routines operate on a smaller amount of vertices (no duplication of vertex transformation of adjacent cubes).
This sacrifices some flexibility, as in STI's engine cubes can added and removed on the fly, but it makes the code much more streamlined, considerably faster and general purpose.
I had to tweak a few things, one of them being that the POV build system used the PsyQ tools, which are incompatible with the Sega Cartdev + Mirage development system. I worked a little on the code, which was setup to load all assets from the PC host through the PsyQ SCSI interface, rather than from the CD (or the CD emulator).
Once that was fixed, I had to find a way to change the build scripts so that they would output something other than PsyQ's proprietary CPE format, so that I could test on the Cartdev.
Then I had to find the raw data and reconstruct the build environment with the correct tools to build the actual binary data that goes on the disk.
After I was able to run everything, it was downhill, a couple more fixes to the code and the build ran just fine...
Enjoy!
Jolly