OpenGL locationInView co-ordinates

[QuantumDoja]

Hi, I want to use touches in an opengl app, the problem is the co-ordinates system.

In open gl, I can draw a point at 0,0...which is the center of the iphone screen, however, touching the screen has coordinates from the top left corner at 0,0.

So my question is, How can I either shift the registration point of the opengl system 0,0, to match the top corner of the screen, or write a system to convert between the points...Has anyone got any example code?

Thanks!

[QuantumDoja]

hmm, its all about where the reg points are:

glOrthof(-1.0f, 1.0f, -1.5f, 1.5f, -1.0f, 15.0f); middle
glOrthof(-1.6f, 1.6f, -2.4f, 2.4f, -1.0f, 15.0f); middle
glOrthof(0, rect.size.width, 0, rect.size.height, -1, 1); bottom left