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gmane.games.devel.opengl |
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Fat City Network Services, San Diego, California |
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<[email protected]> |
Hello all,
I would like to know more ins and outs of 'cumulative rendering' in
OpenGL. With cumulative rendering I mean rendering over the previous
frame, without a clear.
I am working on an application that generates complex imagery, pixel
by pixel, and I would like to update only the pixels that have changed
between the previous and the current frame. I understand I will still
need to update the complete image in case another window, or my GUI
draws on top of the image. That's taken care of, no problem.
A single buffered GL context seems ideal for this, but sadly this won't
work on OS X using glut... A glutSwapBuffers() seems necessary to make
the rendering visible on screen. On Linux and MS Windows, this works fine.
So I have chosen a double-buffered context, and it turns out that the
back buffer is identical to the front buffer after swapping, which is
exactly what I need. But according to the GL spec, this is not
guaranteed, but depends on the driver and swapping mode in use.
Is it possible to use glCopyPixels() to copy the front buffer to the
back buffer after a swap? If so, this would make sure the initial
conditions for the new frame are ok.
Or are there other solutions available?
Erwin Driessens
Driessens & Verstappen
www.xs4all.nl/~notnot
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