[Gzz] Nadir

[Tuomas Lukka]

I tried nadir today (make runbuoydev), and it looks VERY nice.

For presenting it, I only have one huge problem now: the most natural
location of the nadir depends on the location of the viewer!!!

If looking at a close distance, the nadir has to be close, and if far,
it should be further, making the rotation smaller. In fact, I presume
that in eye terms it's a constant angle from the location of the focus.

We should investigate the optimal location.

The problem, of course, is how to do this right for a roomful of people
on a projector ;)

        Tuomas