Thanks so much! But I got another question:
I don’t know how to link a picture here, so I have to add an attachment, it’s a picture, and I tried to draw a picture like this. here is my code:
test()
{
TF3 * f1 = new TF3(“test1”,“x2+y2+sqrt(([0]2+[1]2)*(x2+y2)+4*[0][1]xy)-z",-5,5,-5,5,-2,10);
TF3 * f2 = new TF3(“test2”,"x2+y2-sqrt(([0]**2+[1]**2)(x2+y2)+4*[0]*[1]xy)-z”,-5,5,-5,5,-2,10);
f1->SetNpx(50);
f1->SetNpy(50);
f1->SetNpz(50);
f2->SetNpx(50);
f2->SetNpy(50);
f2->SetNpz(50);