how to draw a potato shot through by a bullet?

Hi all:
My question is as obvious as the title says.
I am doing something like a CAD. I have put a mountain there and now i want to make a tunnel through it. I found it is quite complicated to update the faces of the mountain which intersect with the tunnel.
Thanks for any hint!

I would say model the mountain in a modeling program such as 3d studio max or milkshape and manually cut a whole in it, then load the model into your program and use it as the moutain. This is the easiest way unless you want to perform your own CSG functions to manually cut triangles, it’s a pain to learn and code, i’ve tried.

If all that you want is to DRAW the
mountain and the tunnel, take a look
at this:

Search for

If you want the geometry this will not help.