Sorry for that! The first picture was taken from DWG TrueView 2018 and the second one from your sample OpenGL...CS. The original DWG file I already sent it to you with my first message. As I said before the same DWG file exported to Ascii DXF R13 is not shown in your sample OpenGL...CS.

I've refined the edge visibility a bit for polyface mesh entity rendering, please download the latest CadLib 4.0 version. - Wout

That's exactly what I was looking for! Impressive! Thank you very much! The change will stay in the official version of the library? Do I need to change something else? Regards, Radu G.

Yes, I made the change to the regular CadLib version (there is no other version anyway). - Wout