I've wanted to write a GLES 2 map renderer for ages -- ever since I saw that the Apple Maps app on iOS uses MSAA for antialiasing (yuck!).

It's funny to see all the usual 2D suspects in the source (clipper, GLU tessellator). They used a distance-based edge shader for antialiasing, so it should look much better than MSAA.

I'm not sure why there's a bias factor of 2 in the "raster" fragment shader -- looks like it might have been added by accident. It's interesting that they use both the stencil and depth buffers for clipping -- I hope they do a write up on some of the techniques they developed!