Need some answers!

[dimensionX]

Is it possible to read information from the accumulation buffer or write information to the accumulation buffer from inside the pixel shader ?

Is it possible to copy information from the z-buffer into a 2D texture ?

Is is possible to copy information from the accumulation buffer into a 2D texture ?

Is reading a 3 x 3 size array from frame buffer and updating a 3 x 3 portion of an existing texture (ex:- glCopySubImage2D()) FASTER than using pBuffers ?

I am using NVIDIA QuadroFX 3000. Any comments suggestions would be greatly appreciated. Thank you!

[Relic]

1.) No.
2.) Yes. glCopyTexImage2D with internalFormat GL_DEPTH_COMPONENT[16,24,32]
3.) Not directly. Only color and depth buffers can be sourced, not accumulation buffers.
4.) Don't know, bench it. glCopyTexSubImage2D with misaligned sizes can be slow depending on how textures are handled in different implementations. With pbuffers you mean render-to-texture pbuffer?

With floating point buffers you can implement your own accumulation buffer.