Why does fimplicit3 provide an empty plot?

Hello! Can anyone tell me why the second plot in the image below is blank? Is it because the implied radius is 0?

The first ellispoid is visible, but the second is blank. I fiddled with the intervals, but X and Y always display as shown (-0.5 to 0.5?).

f = @(x,y,z) x.^2 + y.^2 + z.^2 - 5;
fimplicit3(f)

f = @(x,y,z) x.^2 + y.^2 + z.^2;
fimplicit3(f)

Thanks in advance for any suggestions!

Answer 1

[John D'Errico]

The second equation does indeed have has an implied radius of ZERO. So the solution is a single point, where x=y=z=0. It is the equation of a sphere with a radius of zero. Perhaps fimplicit3 missed the subtlty of plotting a single point, or perhaps it did, and just made the point so small as to be invisible, since in reality, a single point is no more than that.

[John Bleichert]

I think it probably plotted a point, which is not very visible. Thanks!