import graph3; import palette; size(200); currentprojection=orthographic(6,8,2); real c0=0.1; real f(real r) {return r*(1-r/6)*exp(-r/3);} triple f(pair t) { real r=t.x; real phi=t.y; real f=f(r); real s=max(min(c0/f,1),-1); real R=r*sqrt(1-s^2); return (R*cos(phi),R*sin(phi),r*s); } bool cond(pair t) {return f(t.x) != 0;} real R=abs((20,20,20)); surface s=surface(f,(0,0),(R,2pi),100,8,Spline,cond); s.colors(palette(s.map(abs),Gradient(palegreen,heavyblue))); draw(s); draw(zscale3(-1)*s); axes3("$x$","$y$","$z$",Arrow3);