{
   auto c2 = new TCanvas("c2","c2",600,400);
   auto f3 = new TF3("f3","sin(x*x+y*y+z*z-36)",-2,2,-2,2,-2,2);
   f3->SetClippingBoxOn(0,0,0);
   f3->SetFillColor(30);
   f3->SetLineColor(15);
   f3->Draw("FBBB");
}