[Inkscape-user] Complex gradient that follows a path?

I'm trying to make a simple illustration that involves some three dimensional shapes (specifically prolate and oblate spheroids). I tried to do this ink Inkscape but found myself unable to make the gradients that seem to be required to show the 3D shape. I'm looking for something like this:

http://www.maths.leeds.ac.uk/Applied/research.dir/Bio/sc0.gif

Notice that the lines of constant color are not linear or elliptical, which is all I can seem to get from Inkscape gradients. I suppose I need to be able to create a path and say to the gradient tool "Make the lines of constant color follow this path."

Suggestions about how to do this, or what tool I should be using to do this, are welcome.

Thanks! Greg