Is it possible to save/load the depth buffer (without the use of shaders)? I was recommended to use glCopyTexImage to save the depth buffer into a texture, but no idea how to load it back…
Simply using glReadPixels (save) and glDrawPixels (load) with GL_DEPTH_COMPONENT should do fine, no need for glCopyTexImage.
Check the man page for details: http://www.opengl.org/sdk/docs/man/
However the drawpixels will fill both depth and rgba, with current color.