Breaking complex polys into quads

Has anyone come across any code to take a 2d shape and break it into quads?

I need to be able to bring in some urban area shapes and break 'em down into rectangles/quads.

By texturing each quad and aligning each texture with the quad's longest side, I think I can then make it appear as though there's structured housing from a distance (rather than just applying one blanket texture across the entire urban area).

But how can I break down the complex shapes?

Oh well - I've decided to do it manually - in a design package. Don't have the time to fiddle about finding an algorythm.