I've been searching around the internet for a while now and I'm not finding the answer to my question so I thought I'd give this a whirl...

All I want to do is click on a point in my application's window and have the app draw a dot at that point. My problem comes in when I use the coordinates I get from unprojecting the mouse click to draw the point. The window size is 600 x 600 but my viewing area is set up as glOrtho(-30, 30, -30, 30, -10, 10)

Is there a way to unproject the mouse click to the glOrtho coordinates? If there is, does it lose too much accuracy?

Thanks for any help!!