%http://www.mathcurve.com/surfaces/coquillage/coquillage.shtml

input mp-solid

%16''
figureespace(-100u,-100u,100u,100u);
Initialisation(1500,0,20,60);
outcolor:=0.5[vert,blanc];
incolor:=0.5[jaune,blanc];
angx:=180;
k:=3;
m:=1/10;
a:=1;
b:=a*abs(exp(m*pi)-1)*(1++k)/(exp(m*pi)+1);
draw Sparam("RotXYZ(((a+(b*cos(v)))*exp(m*u)*cos(u),(a+(b*cos(v)))*exp(m*u)*sin(u),(a+(b*sin(v)))*exp(m*u)))",5,-30,-0.125,0,2*pi,pi/8);
finespace;
end