Having a set of camera intrinsic parameters, how can I simulate lens distorion in OGL?
take a look at this presentation http://mirror.ati.com/developer/gdc/GDC2003_ScenePostprocessing.pdf
and this source (directX, but you can still see how it is done) http://mirror.ati.com/developer/samples/dx9/DepthOfField.html
maybe this will help a little bit.