import graph3; import palette; size(200); currentprojection=orthographic(4,2,4); currentlight=Viewport; real r(real theta, real phi) {return 1+0.5*(sin(2*theta)*sin(2*phi))^2;} triple f(pair z) {return r(z.x,z.y)*expi(z.x,z.y);} surface s=surface(f,(0,0),(pi,2pi),50,Spline); s.colors(palette(s.map(abs),Gradient(yellow,red))); draw(s);