How do you build a tunnel that cuts into the terrain?

#1 In the terrain editor go to Action/Set Empty

#2 Start the editor choose the "terrain editor", in the action menu select "set empty". Experiment with brush size and settings until you get the control you want. Try making the entrance to your tunnel thick walled to help fit the hole.

edit
ben beat me to it

#3 It also works better if you're working on a larger scale than the default. We did a racing game in 5X scale, and that way the terrain blocks looked small compared to the interiors and models, allowing us to cut the terrain more accurately.

#4 Following up to this: set empty removes a square, you don't seem to have control about the size of the square. Is common practice to just design an entrance to fit perfectly around the square, trial and error to get it right?

Manoel, this is a complete basic question, but could you explain what you mean by 5x scale? What is your reference for scale?

#5 I think what he meant is that he multiplied the size of all his shapes by 5 so it made the terrain blocks appear smaller.

edit: typo

#6 I strongly suggest you to NOT change terrainsquaresize, for ANY reason. Add rocks, enlarge blocks, do whanever is necessary to fill the gap on the terrain, but DON'T change the squaresize - this feature is deep encrypted in the assembler routine of torque code and often messes up with everthing inside the game. trust me on this one.

#7 Probably the best thing you could do is just place some static DTS shapes around the interface of the terrain opening and the cave (which I would guess is a DIF).

#8
From here