Switching between 2D AND 3D

How can I draw on the same form in 3D AND 2D.
What I want to do is if there is a 3D object on the screen I want to draw a rectangle with the mouse to do a zoom of that rectangle

Wat I mean :
How can I make a rubberband rectangle to make a selection on an OpenGL screen

  1. Look at glOrtho for 2D, and theres no problem in mixing parallel projection with perspective projection on the same scene.

  2. This isn’t an advanced question, so better post it in the beginners forum