During some free time, I decided to boot up the Japanese version of Sonic Adventure on an HKT-01 Dreamcast Development Box. Running the game off the hard drive made it easier to edit/hack certain files of the GD-ROM data instead of wasting numerous CD-R discs. While running GD Workshop, the application used to build a GD-ROM project, I went ahead and saved a log of the data files that were being executed while running the game. From there, I was able to determine which files were being used on certain levels.
After analyzing the log that was generated, I got a little bored and decided to edit/remove a few files to see what would change. One difference I noticed when I removed a certain .PRS file used in the stage Red Mountain was that there was an entirely different level texture in substitute of the removed texture. I was also able to remove certain .BIN camera files to alter the camera angles assigned to the levels.
There was a lot to learn from checking the log file that was being generated while running the Dreamcast game, but not all of the hacks I attempted worked out flawlessly. Some would reboot the game entirely!
Source: http://www.segakatana.com/forums/viewtopic.php?t=85
