I want to project the globe onto a 2D projection (Mercator). This is no probs but the projection I require has the projected y value kind of stretched Northwards (above the equator) and southwards (below equator). The stretchiness is non uniform. How do I represent a projection like this in OpenGL? For your info, the y value modification formula is:

y’ = log(tan(PI/4 + y/2))