[PyOpenGL-Users] Calling pyopengl developers.. PBO problems.

[qzm <stu...@gm...>]

Well, its been over 6 MONTHS since I pointed out this rather major problem
in glreadpixels, and so far no reaction?
Does anyone else find this a problem? without it we cannot use PBO (pixel
buffer objects), which is a major addition to the opengl spec, and gives
access to a whole range of important new functionality.

It really would be nice to stop having to use custom C python extensions
that need maintennce just to allow this one call..

>From: qzm <stuartaw@gm...>
> glReadPixels spec problem.
>2005-02-28 16:42
> Hello fellow pyOpengl Users.
>
> Perhaps I am missing something, but Ithink there is a serious issue
> with glReadPixels.
>
> When using glReadPixels in combinations with pixel buffer objects
> (PBOs) the last (C) argument is no longer the address of memory to
> move the data to, but an offset from the currently defined buffer
> object base.
>
> As a trivial example it is connon to use:
> glReadPixels(0,0,640,480,GL_BGRA,GL_UNSIGNED_BYTE,0)
> Which causes the data to be copied to the base (0 offset) of the
> currently defined PBO.
>
> Of course, in pyOpengl this does not seem doable, as the buffers are
> handled internally, and the last argument is not exposed.
> Is it possible that we could have new versions of the affected calls
> exposed that do take the last argument?
> Perhaps a glReadPixelsB (for buffer) or something like that?
> (glWritePixels has the same limitation).
>
> PBOs are a very important feature for using openGL in image
> processing, so this would be a very useful addition.
>
> It would also allow glReadPixels to be used from python in situations
> where the overhead of the double data copy currently required for the
> (much easier to use) current implementation is too much whem moving
> through bounce buffers.