Hi I see you're new! Welcome to the forum roadkill
I'm Atrox and I'm one of the moderators here. You should make a thread in the introduction section to introduce yourself to the rest of us!
Also in the future, please try to keep all posts relevant to the thread you are posting in. If you want to compliment someone's picture, we have a nifty little shoutbox at the bottom of the website, or you can send alexthe666 a private message. Thanks!
Ever played around with skydomes in gmod? On the outside, they are invisible, but the inside is visible. To make burrows, we would just make a tube that disables world collision, and looks visible on the inside.
It's not that simple. In Thrive we don't just have to make a world, but make a system that makes and develops worlds themselves -- so we can't just use some authoring tools and make a burrow mesh etc, we have to make a system that generates reasonable burrows. How we do that, is the question.
A good idea would be to have the terrain be a simple height field (converted to a polygonal mesh), but have the caves and burrows be made of voxels that will be smoothed using marching cubes. That would allow for their dynamic editing and overhangs.