I display the scene in a normal rectangular window.
I want to display my scene on the screen in a circular viewport. I mean the scene will be viewed within a circle. Can anyone know how to do that with OpenGL C++ environment?
You could try playing around with the FOV (Field of View) value for gluLookat. Extreem values (towards 0 or 180) will give fish-eyed look to the viewport and distort the display - like a circular viewport!