why do I need to add eps ?

hello I want to ask why do I need to add the value eps to this code ?

   x=-8:0.5:8;
   y=x';
   [xi,yi]=meshgrid(x,y);
  r=sqrt(xi.^2+yi.^2)+eps;
   z=sin(r)./r;
  mesh(x,y,z,r)

becouse for some reason if I do not add eps i get a hole in the top, why is that ?

Answer 1

[Andrei Bobrov]

To avoid the uncertainty of "0/0" situation when calculating z.

When x = 0 and y = 0.

[tomer polsky]

ohh ok thank you very much