I am modifying some existing code that has a 2D orthographic projection set as:
glOrtho(-0.02, 1.02, -0.02, 0.68, -1, 1);
I have never had an issue with transfering pixel coords (mouse clicks specifically) into world space when the left/right, top/bottom values of the frustum are symmetrical.
I simply convert the pixel values to a normalize -1 to 1 'window coord' centered in the middle of the window and then scale those values by the right/top values given to my frustum.
But for some reason I am getting really confused when converting to this asymmetrical frustum.
This should be simple, but I can't for the life of me figure it out!
I feel silly now, I figured it out:
// normalized window coords centered on bottom left of window float x = (pixel_x / window_width); float y = (window_height - pixel_y)/(window_height); // world coords by scaling and translating x = x*(frustum_right - frustum_left ) - frustum_left; y = y*(frustum_top - frustum_bottom) - frustum_bottom;
Edited by pondwater, 17 January 2013 - 05:54 PM.