import solids;

size(7.5cm,0);

currentprojection=orthographic(3,9,2);
currentlight=White;

revolution sph=sphere(O,1);

real a=.7; //compris entre 0 et 1
real b=2.4;
draw(surface(shift(-b/2,-b/2,sin(pi*(a-.5)))*scale3(b)*unitsquare3),white+opacity(.7));
draw(surface(sph),orange);

skeleton s;
sph.transverse(s,reltime(sph.g,a),P=currentprojection);
draw(s.transverse.back,linetype("8 8",8));
draw(s.transverse.front);