Fix bug in smooth ceiling mode

The ceiling calculations for the gradient factors still had a 3m increment
hardcoded. This is now also conditional on the smooth parameter.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Stub out a few things for a plan input UI

This is not doing anything (which is why there are so many unused variable
warnings). It's just a couple of entries lined up to give a visual
impression how some of this could look.

I am not a UI designer. And there are good reasons for that...

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>