Coordinate System: how to change?

Hi all!

The default OpenGL coordinate system, in 2D, is (-1, 1) in the upper-left
corner of the windows and (1, -1) in the bottom-right corner. It is
possibile to change this system? In particular, I need to have a coordinate
system in which (0, 0) is the upper-left corner and (640, 480) the
bottom-right corner.

Thanks in advance,

Marco Minerva,

Read about projection modes and glOrtho. You have to understand how they works and then you’ll manage the problem.

And to handle the upside-down aspect of things, take a look at glScale. Scale your image by -1 in the direction you want to flip, then translate the coordinate system back to where you want it.

While fiddling with all these things, it’s easy to get directions mixed up. I recommend drawing four lines that lie just inside where you expect the visible area to be - that way you can immediately see whether things are correct or not.