It looks, misleadingly, like the curvature remains bounded at the corner, like the three planes of a corner cube. But no, the corner is kinky <http://gosper.org/verycross2.png>. With planarizing, it could sill make a decent corner cube. —rwg "Fresnel corner cube" <http://gosper.org/martinsmarbles.png>. I've always wanted to mount a big corner cube anemometer on my car's roof to spoof police radar. "But it's my airspeed indicator!" On Tue, May 5, 2020 at 12:25 PM Howard Cohl <howard.cohl@nist.gov> wrote:

That's really neat.

I wonder if it has a name. Also, are there analogues for other knots?

There must be, eh?

-- http://www.nist.gov/itl/math/msg/howard-s-cohl.cfm

On 5/4/20 4:55 PM, Bill Gosper wrote:

Does this thing <https://gcc02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgosper.org%2Fverycrosscap.png&data=02%7C01%7Choward.cohl%40nist.gov%7Cb12e319bdc124f10dc6808d7f0869ac0%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C0%7C637242333222901555&sdata=sBPWOTNweHRWg%2FGSilRfYOl%2FlrZNydBk5VodxdvkbNs%3D&reserved=0>have a name? —rwg

ParametricPlot3D[{(1 - t) Cos[2 u] (3 + Cos[3 u]), (t - 1) (3 + Cos[3 u]) Sin[2 u], 4 t + (1 - t) Sin[3 u]}, {u, -π, π}, {t, 0, 1}, ViewPoint -> Below]