Can you have 2d ortho perspective and 3d perspective both on screen

[new hope]

So i was coding up some c++ for a UI and while i could display the UI in a 3d perspective with opengl and just not translate it during movements in the 3d world i think it would be more accurate to display it in 2d that way it is as "close" as possible. But can i set it up as a 2d view after the 3d view has been rendered that way it overlays the 3d view? If so how would i code it. I imagine i would just render the 3d scene then call the function to change the perspective and render the 2d graphics.