Can I read data from buffers of a AGP card.

[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. Is that true?

Thanks in advance,

Darron

[pkaler]

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).]

[darron]

Originally posted by PK:
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).]

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

[fenris]

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.

[darron]

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.