how to get value from opengl calls

hi every body,

I’m beginner in opengl and I need an immediate help because my due is the day after tomorrow. we are supposed to implement z-buffer and flat - gouraund- phong shading and this is the hint from the insrtuctor :
“you may use opengl to
you pass coordinates of a 3D point and you can ask
> opengl to give you the 2D coordinates of the projected point. From then
> on, you are to implement rasterization and other steps.”
how can i take values of the 2D coordiante and the Z’ (for z-buffer)
from opengl call.

I appreciate your quick answers.


To get the window coordinates from an object coordinate you can use gluProject. Look at this thread for more information. To read the depth buffer (z-buffer) you can use the glReadPixels function.

Edit: After rereading the thread that I give you the link, you do not need to call glReadPixels because the value of the depth seem to be included as WinZ.