Anyone interested in rendering geographic data with opengl! please help me

As you know we have two kinds of coordinate systems in GIS : Geographic coordinate systems and projected coordinate systems

consider these situations:

I have a shapefile that has projected coordinate system, I mean the coordinates of the vertexes are in PCS, so there's no problem I can extract vertices with GDAL/OGR library and then show them in OpenGL with orthographic projection. since the coordinates are in meters and they're projected on a 2D plane, there will be no problem I think.

The datasource has a geographic coordinate system and I just want to render it in a projected coordinate system, so I have to do the transformation with PROJ.4 library and then render the transformed coordinates in OpenGL. Again I think there will be no problem, since the coordinates I want to show areb projected on a 2D plane.

The datasource has a geographic coordinate system and I want to render them in the the same GCS on an OpenGL window. So I extract coordinates with GDAL/OGR in geographic coordinate system and without any transformations, I'll render them in OpenGL. How can I achieve this? I mean how can I set up an ellipsoidal plane in an OpenGL window just like ArcGIS does renders data in geographic coordinate system?