How to implement 'zoom' when designing an orthographic view base application. I would prefer if there is a way where we can move camera in/out on screen axis to perform zoom. It's similar to commercial 3D application like Maya or 3ds max where you an move the orthographic camera.

I have tried using 'glScale' but it doesn't meet my requirements. 'glOrtho' doesn't support camera position. Do I have to go for 'glPerspective' ?