I discovered this issue after playing it and from what I understand, this game's shadows do not render, even after fooling with the config files.

According to an old thread:
https://forums.geforce.com/default/topic/353473/pc-games/advent-rising

This game's shadow system only worked on an ATI 9800 Pro card and did not work on NVIDIA cards of the time. I am not sure if the game is broken on modern AMD cards so if you have one and this game, try it out and let me know. I can say with confidence that this game is broken on NVIDIA cards in the shadow department and I can not find any solution as of yet.

While I do pose the question of how to fix the shadows once and for all, I wanted to post this as a problem to raise awareness of this issue for this underrated classic.

I posted this for awareness so maybe someone can figure out how to get the shaders to work on any GPU. With the rise of dgVoodoo2 being able to make the first 2 Splinter Cell games have their respective buffer shadows to work, there is a chance this can get fixed too.