Unity is not a voxel engine, but it has several packages that allow me to fudge it decently. I am using this package
for voxels and some others for gameplay logic. I think you'd have to be insane
to try to make a high quality game out of this stuff, but for a ten minute vertical slice, it'll do.
Meanwhile, I have a lot of people asking me things like, "OK what kind of
puzzle will you have in your game? What kind of
combat?" Even though my game idea is more by-the-book than something Jonathan Blow might make, there's still some stuff than needs proving. I don't want to wait for the model import / scene graph / animation queue / sound systems to be done before answering those questions.