Can I read data from buffers of a AGP card

I need to read things from a buffer of my video card using openGL. A friend told me that I can’t do that with my AGP card. Is that true?

Thanks in advance,

Darron

Originally posted by darron:
I need to read things from a buffer of my video card using openGL. A friend told me that I can’t do that with my AGP card.

Which buffer? Color, stencil, depth, etc.

Reading back is kinda slow, but still doable. Take a look at glReadBuffers and glReadPixels.

[This message has been edited by PK (edited 12-30-2002).]

Originally posted by PK:
[b] Which buffer? Color, stencil, depth, etc.

Reading back is kinda slow, but still doable. Take a look at glReadBuffers and glReadPixels.

[This message has been edited by PK (edited 12-30-2002).][/b]

The reason I asked that question is because a friend told that AGP bus is a one-way bus: you can only send data to graphics card, can’t get them back. If possible, I’d like to read from all buffers.

Thanks,

Darron

Your friend probably just told you that to save you a little frustration. Reading back data causes pipeline stalls, and can be very slow. Recently NVIDIA has exposed the NV_pixel_data_range extension to speed of this very type of operation. It should be available on all Geforces. If performance is of any relevance to you, I suggest reading up on using this extension.

I am using TNT2. I just need to read a couple of pixel. Is that a big problem? And I also need to and the contents of the buffer, is that easy to do with openGL? Thanks in advance.

This topic was automatically closed 183 days after the last reply. New replies are no longer allowed.