Show HN: Eggspression – shape any bird egg in 3D from four parameters

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Eggspression

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Eggspression

every egg is an expression

Eggspression

An interactive 3D egg you shape with four numbers. Every bird egg — from a near-spherical<br>ostrich to a sharply conical murre — is one surface revolved around its long axis, and a single<br>equation describes them all.

The formula

It renders the universal egg formula of Narushin, Romanov & Griffin (2021), which<br>unifies the four classic egg geometries — sphere, ellipsoid, ovoid and pyriform — as special<br>cases of one profile y(x). Four parameters drive it:

L — length, tip to tip.

B — breadth, the widest diameter.

w — asymmetry; shifts the bulge toward the blunt end (0 = symmetric).

D — the diameter a quarter-length from the tip; the term that lets the curve taper into<br>a conical/pyriform shape.

Narushin, V. G., Romanov, M. N. & Griffin, D. K. (2021).<br>Egg and math: introducing<br>a universal formula for egg shape. Ann. N.Y. Acad. Sci. 1505, 169–177.

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Length L<br>Long axis, tip to tip

Breadth B<br>Widest diameter across the middle

Asymmetry w<br>Shifts the bulge toward the blunt end — 0 = symmetric

¼-length Ø D<br>Diameter a quarter-length from the tip; lower it for a conical/pyriform egg

Mesh detail<br>Triangle density of the 3D surface

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specimen no. 1 · s13k.dev · formula: Narushin, Romanov & Griffin 2021

length eggspression shape from four formula

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