Tron was a mix of CGI and not-CGI. The not-CGI stuff, w/ all the photographic technique, was pretty wild. The CGI, in contrast, was not as wild.

I believe this was the documentary I watched a couple of years ago re: the making of Tron that went into a lot of detail about the effects: https://www.youtube.com/watch?v=sbgHMrLPQrE