This nautilus style shell is my contribution to Project Shellter. Hopefully my brother's hermit crab will like it. I know we already have a nautilus shell on Thingiverse but this shell is pure OpenSCAD, drawn piece by piece with polyhedrons using a formula which approximates the fibonacci spiral. I made the first chamber very large, hopefully large enough for a hermit crab to wrap it's abdomen around. Just for fun, I have included photos of my (mostly useless) rough math notes.

DISCLAIMER: Unfortunately, it would be a lie to say it's parametric. It is, but the range of parameter values that don't crash OpenSCAD while rendering is small. It previews and looks fine with a wide range of values, but crashes while rendering with most values. Also, it only renders with OpenSCAD > 2011.06

Print both halves and glue together. The overhangs are brutal. The best advice I can give is to print fairly slow with a fan for the whole print (overhangs the whole time!) except the first layer.