Horizontal terraform

Would it be possible to terraform horizontally? I am not sure if the spring engine would support it because maps are done with heightmaps and not models. I am just throwing the idea in the air here, if it would be possible I think it would add an enormous amount of tactical depth to the game. Imagine digging a tunnel under the enemy base and filling it with roaches.

quote: maps are done with heightmaps and not models.

There's your answer. Besides, even if it was a model, it would still likely be impossible. Don't quote me, but you might need nothing short of a voxel engine to do this.

There has been an initiative to extend the Spring engine to do just this years ago, but it never went off. Or am i mistaken?

Ya, I saw the bridge too. Was pretty cool. Would be awesome if some mas made use of that.
I am pretty noob to coding and stuff, but would 'underground' not be like the same as underwater mechanics?

oh my gosh.. just think of the pathing on actual 3d maps *shocked*

Terraform is just perfect as it is.
But bridges would be awesome