I’ve been working on a C# reimplementation of the GTA: 3D era engine as a side project for the past few years.
I am not trying to create perfect copy (we got reverse engineered versions for that), just my own simplistic version that can parse most of the files and play missions.
Currently, the project can render the III and VC map, play animations and run a big part of the main script (with a lot of missing opcodes) and run cutscenes. With some of those things working better than others.
A few years ago I’ve created and uploaded a couple of short clips that showed the first progress. They can be found on my YouTube channel.