Hi Rix and Matthäus,

Evan is right. If sleep() affects your ReadPixels() result,
something is probably wrong in the driver. (Unless you're using
an asynch extension like PDR that requires the app to use fences
or similar.)

Perhaps you can contact me offline?

Thanks -
Cass

> -----Original Message-----
> From: ml-errors@... [mailto:ml-errors@...] On
> Behalf Of Evan Hart
> Sent: Friday, October 07, 2005 10:39 AM
> To: Multiple recipients of list OPENGL-GAMEDEV-L
> Subject: RE: GLSL + 6800 + Multiple steps by frame
>
>
>
> Actually, assuming that the read is done with a normal
> glReadPixels, neither glFlush nor glFinish are required,
> because OpenGL commands are guaranteed (to appear) to
> complete in-order given a single context. It sounds like a
> driver bug to me, or you are doing something that explicitly
> allows synchronous operations and not accounting for it.
>
> -Evan
>
>
> -----Original Message-----
> Sent: Friday, October 07, 2005 3:09 AM
> To: Multiple recipients of list OPENGL-GAMEDEV-L
>
> You need to call glFinish (), not glFlush (). glFlush ()
> means that all
> commands are passed to OpenGL for processing - not that the
> processing
> has finished (for example, if you use OpenGL via Network, glFlush ()
> send all commands in a packet). glFinish () on the other hand
> does wait
> until the rendering has finished.
>
> Cheers
>
> Matthäus Chajdas
>
> Rhadamés Carmona schrieb:
> > Hello Everybody
> >
> > I am programming with 3D textures and GLSL. At some point, I was
> > interested
> > in making 2 renderings in one frame, for comparrison...
> >
> > void DrawScene()
> > {
> > glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
> > Render();
> > glFlush();
> > ReadFrameBuffer(A);
> > glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
> > Render();
> > glFlush();
> > ReadFrameBuffer(B);
> > difference = B-A;
> > // Do something with difference, here!....
> > glFlnish();
> > glutSwapBuffer();
> > }
> >
> > The second rendering is not correct... I get a mess. But,
> If I put an
> > Sleep(200) after every glFluch, everything is ok!.... Coudl
> you give me any
> > clue about what the hell is goiing on?
> >
> > Cheers Guys!
> >
> > Rix
> >
> > Note: I am using latest drivers....
> >
> > -----
> > FAQ and OpenGL Resources at:
> > http://www.geocities.com/SiliconValley/Hills/9956/OpenGL
> >
> -----
> FAQ and OpenGL Resources at:
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>
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-----
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--
Author: Cass Everitt
INET: CEveritt@...

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