pbuffer
GLXPbuffers are additional non-visible rendering buffers for an OpenGL renderer.
They can be volatile or non-volatile.
High IMPACT will support pbuffers in the depth buffer. Use of pbuffers
on this configuration is discouraged, if planning to run depth buffered
contexts.
Maximum IMPACT will support pbuffers in an auxiliary buffer.
Drawing into pbuffers on IMPACT will be fast unless multiple contexts are
in contention.