I built an 8' wide spherical display out of an advertising balloon, a hemispherical security mirror, and a conference room projector. Then I wrote a 3D engine

I built an 8' wide spherical display out of an advertising balloon, a hemispherical security mirror, and a conference room projector. Then I wrote a 3D engine that could render to it and took the whole thing to Burning Man. Worked pretty well, though contrast was crappy.