Line extra thickness in PDF/EPS

The save pictures is very good in .png format but when it is in .eps or .pdf the very thin lines used in 3D surface meshing become very thick and dark that detoriated the quality of the image. I think it is due to fixline subroutine. Please suggest the changes in code so that I could maintain the thickness of mesh-lines in .eps format. Moreover, I want that hidden lines/surface should not come over, So how can I do that. Thanks