stencil shadow artifacts - doom 3 engine - along bounds of light/shadow volumes

Hello, I have been testing the maximum map size of the Doom 3 Engine (GPL release -

Everything was working well, until I started noticing these shadow artifacts:
at position: -10901 -18214 -11204

The farther away from the origin I get, the more pronounced these artifacts are:
at position: -10802 -26483 -19383

at position: -10802 -34683 -27540

It seems that all of these artifacts are along the light/shadow volume bounds.

I have had limited success trying to test where the problem is occurring in the source - it seems to relate to whether the shadow volumes are capped - as disabling capped shadow volumes seems to get rid of the artifacts - but causes some other equally visible artifacts.

But in general it is all Greek to me.

I am looking for someone to point me in the right direction for how I could start learning how to solve this kind of problem. Should I just start reading stencil shadow tutorials, or should I start at the beginning with beginning OpenGL tutorials?

I feel like in the end I will find that it is not so much a bug as it is a trade-off with performance - but I am willing to make that trade off.

Also, any information about prior experience with this kind of problem will be helpful to me.

More examples:


I did finally find a solution - see here: