A torus can be defined parametrically by:
where θ, φ are angles which make a full circle, so that their values start and end at the same point, R is the distance from the center of the tube to the center of the torus, r is the radius of the tube.
plot3d( [ ( R+r(u,v)*cos(v))*sin(u),
lightmodel=light3, viewpoint = circleleft);
I set range [-5..5] of the Z axis，but the range of Z axis tickmarks in the above image maybe in [-4.5..4.5] .
How to have tickmarks included at -5 and 5 on the Z axis?