Re: cumulative rendering

> To do this properly, you need to run single-buffered.
>
> I believe GLUT supports that - but don't call glutSwapBuffers - use
> glFinish() instead. (I'm a little hazy on this one - it's been a lot
> of years since I last used GLUT with single-buffering!)

Ok, I have found out that a single-buffered GLUT setup works in OS X
when I use glFlush() instead of glutSwapBuffers(). But what will happen
if my window is overlapped by another window? I will try and see what
happens.

>> Is it possible to use glCopyPixels() to copy the front buffer to the
>> back buffer after a swap?
>
> No - because your window might be overlapped (in which case part of the
> front buffer will have been trashed by the other window) - or the graphics
> card may have done processing on the back buffer as it swapped it into the
> front buffer (eg for antialiasing).
>
> However, you could copy your back buffer into a texture map before you
> swapped - then copy the texture into the new back buffer afterwards.

Ok, this seems a robust way to solve my problem. The question is if this
mechanism is actually faster than rendering the complete image each frame.
My image is computed (and stored) in main memory, and does not depend on
OpenGL functionality at all (to generate it at least). I found out that
glDrawPixels() is the fastest way to render, faster than updating a
texture and rendering a textured quad. The updated pixels are usually
spread out over the image, so it is not possible to restrict the update
to a small area... I thought: why not render only the changed pixels via
GL_POINTS? Seems an interesting optimization anyway.


Thanks,

Erwin Driessens
Driessens & Verstappen
www.xs4all.nl/~notnot








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