How to specify +/- in a function definition.

[webmasterpdx]

When i use the max function it really slows it down. However, I still think it's a bug. If you plot it with 100 instead of 16 (radius of 10) you'll see gaps up around z=4 or 5....
I'm SURE it's the algorithm, but my point is it's not a good algorithm. Interestingly when I plot it in wolfram-alpha, they do get it right, but you can see the jaggie areas in a slightly different shade, as if it originally plotted it the way mine is, and they filled in the gaps....maybe using max automatically or something.