Writing pixels into an opengl window

This post is based on my recent question, but I got some success, thus here is a
new thread. The old one is:

The main problem is that I have an screen via SDL_SetVideoMode(… SDL_OPENGL)
where I want to write pixels into (I need the OPENGL for my own shaders, which
do some ray tracing support stuff). I recognized two ways how to do it:

Open another screen with SDL_CreateRGBSurface(HWSURFACE…), write my pixels
into this screen with the usual putPixel method from the tutorial and push them
into my OPENGL (here OPENGLBLIT) screen with SDL_BlitSurface(offscreen, 0,
screen, 0). Should work fine, but it happens exactly nothing.

I have only one OPENGL screen and use glDrawPixels() to store pixel manually.
Unfortunately whenever I call glDrawPixels() it segfaults :frowning:

During all my approaches I never saw anything else than black in my window,
which makes me wonder…
Has someone a hint or even a code example for me?
Thanks for your help,

AFAIK the SDL surface functions don’t work on an openGL video surface.

the other problem , 2, needs more elaboration( what are you doing? ),
and i don’t know much about openGL, but any openGL functions i’ve ever
used work with SDL