How to tell what was clicked on? (OpenGL)

I'm trying to make a simple level editor for a game I'm making. Its probably going to be tile based, and I want to be able to click on a tile to select it, then press 1-9 to change that tile to the corresponding number (1 for dirt, 2 for grass, etc). The problem is I don't know how to tell what was clicked on...

Any suggestions would be appreciated!

//napKIN

Try:
NeHe's 'Picking, Alpha Blending, Alpha Testing, Sorting' tutorial (the 'picking' part is what you're after), or GameTutorials Object-Selection tutorial.

Hope that helps :)

Here's an example program from OpenGL Superbible. You'll need GLUT installed to compile.

Awesome, thanks guys!

//napKIN

is that ogl superbible available as a e-book anywhere?