How does the 3D collision extension work internally?

There wasn’t an appropriate tag for this type of question, but this was the closest.

I’m using the extension to code my own 3D physics because the current 3D physics doesn’t do the job for me. And everything works fine, but The character seems to be floating a few pixels above ground when it isin collision with the floor. I tested with a 3D box instead of an object and it doesn’t look like floating, so my guess is that it has to do with how the extension builds the 3Dhitbox for the model. I’ve looked inside the extensions code but the important stuff is in JS which I can only superficially read.