Math of Seashell Shapes

By Xah Lee. Date: . Last updated: .
seashell math 2022-02-09
A mathematical model of the simplest seashell shape.

A simple seashell can be modeled using the following parametric formula:

seashell[u_, v_] := {2*(1 - E^(u/(6*Pi)))*Cos[u]*
     Cos[v/2]^2, 2*(-1 + E^(u/(6*Pi)))*Cos[v/2]^2*
     Sin[u], 1 - E^(u/(3*Pi)) - Sin[v] +
     E^(u/(6*Pi))*Sin[v]};

start = 0;
end = 2*Pi;
gap = 1;
shift = 1;
uMin = 0;
uMax = 6*Pi;
xViewPoint = {1.0992, 3.2001, 0.0255};

gra1 = ParametricPlot3D[Evaluate[seashell[u, v]],
     {u, uMin, uMax}, {v, end - gap + shift, end + shift},
PlotPoints -> {96, 4},
Mesh -> Full,
MeshShading -> {{None},{None}},
PlotRange -> All
]

gra2 = ParametricPlot3D[Evaluate[seashell[u, v]],
     {u, uMin, uMax}, {v, start + shift, end - gap + shift},
PlotPoints -> {96, 20},
Mesh -> Full,
PlotStyle -> Directive[White, Opacity[.8], Specularity[White, 20]],
PlotRange -> All
]

Graphics3D[{ gra1[[1]] , gra2[[1]]},
{PlotRange -> All, Boxed -> False,
 ViewPoint -> xViewPoint}]

wrinkled periwinkle

wrinkled periwinkle 2022-02-10 6Xqm
wrinkled periwinkle 2022-01-21
Formula from Mike Williams mike@econym.demon.co.uk, 2005 Jan.
cR=1; "* radius of tube *";
cN=4.6;  "* number of turns *";
cH=2.5; "* height *";
cF=80; "* wave frequency *";
cA=0.2; "* wave amplitude *";
cP=1.9; "* power *";

cW = ((#/(2*Pi)*cR) &);

seashellF = Function[ {u, v}, {
cW[u]*Cos[cN*u]*(1+Cos[v]+Cos[cF*u]*cA) ,
cW[u]*Sin[cN*u]*(1+Cos[v]+Cos[cF*u]*cA) ,
cW[u]*Sin[v] + cH*(u/(2*Pi))^cP
} ];

ParametricPlot3D[
Evaluate@  seashellF[u, v],
{u, 0, 5},
{v, 0, 2 Pi},
PlotPoints -> {160, 10},
PlotRange -> All,
ColorFunction -> "TemperatureMap",
 BoundaryStyle -> Directive[Black, Thin],
 PlotStyle -> Directive[White, Opacity[0.7], Specularity[10, 20]],
 Lighting -> "Neutral"
 ]

Wentletrap

wentletrap math 2022-02-10 bJg4
wentletrap
Formula from Mike Williams mike@econym.demon.co.uk, 2005 Jan.
Clear[cW, seashell, cN, cH, cP, cA, cF]

cN = 6.6; ("number of turns");
cH = 4.0; ("height");
cP = 2; (" power ");
cA = 0.12;(" Ridge Amplitude ");
cF = 15;(" Ridge Frequency ");

cW = Function[(#/(2 Pi))^#2 ];

seashell[u_, v_] := {cW[u , cP] (Cos[cN u] - cA Cos[cN cF u]) (1 + Cos[v]),
    cW[u , cP] (Sin[cN u] + cA Sin[cN cF u]) (1 + Cos[v]),
   cW[u , cP] Sin[v] + cH (u/(2 Pi))^(1 + cP)};

ParametricPlot3D[
Evaluate@ seashell[u, v] ,
{u, 0, 6},
{v, 0, 2 Pi},
 PlotPoints -> {200,40},
 Axes -> True,
 Boxed -> True,
 BoundaryStyle -> Directive[Black, Thin],
 PlotStyle -> Directive[White, Opacity[0.7], Specularity[10, 20]],
PlotRange -> All,
 Lighting -> "Neutral"
]

Gallery of Shapes

Tightness of Spiral

Outline Variations

Ribs and Folds

Spikes

Internal Structure

Analysis of Seashell Shapes

Seashells are showcasing of spirals. There are great variety of spiral shapes. Suppose we start with a circle winding around a spiral.

• The circle's shape changes periodically like a sine function, creating a corrugated shell somewhat emulate that of

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Paper Nautilus

• If instead of a circle we have a triangle, we can simulate that of

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Top Shell

• If the rounding shape periodically changes shape to have spikes, then we might emulate shells that have horns such as the

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Murex shell

or

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Venus's Comb shell

• The periodic change might also emulate those shell having ribs such as the

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Harper shell

References and Sources

The Algorithmic Beauty of Sea Shells , by Hans Meinhardt, Przemyslaw Prusinkiewicz, Deborah R Fowler. Buy at amazon

Mike Willams has sent me various formulas, see Math Parametric Equation for Seashell

spirals