How do you use maple to plot quadric surfaces like ellipsoids?

The general syntax is:But what if I wanted to plot something like $\displaystyle z = x^2 - y^2 $?Code:plot3d(f(x,y), x = -a..a, y = -b..b)

Does Maple only allow you to plot functions in standard or parametric form?

So you cant type in an equation like $\displaystyle x^2 + y^2 + z^2 = 1 $ and plot it in Maple?