Cool!
I made half a sphere with 0.5+sqrt(0.2-((x-0.5)^2+(y-0.5)^2)).
If there was a way to do a mirroring on the xy plane (as in a +/- z value) it could be a full one.
There's probably a better way to choose which points go above and below than random(), but it works.
Edit: Got it to work non-randomly. Adjacent dots alternate above and below: http://vicapow.github.io/equation-plot-webgl/index.html#0.5%...
http://vicapow.github.io/equation-plot-webgl/index.html#0.48...)
http://vicapow.github.io/equation-plot-webgl/index.html#0.5%2Bsqrt(0.2-((x-0.5)%5E2%2B(y-0.5)%5E2))