Thanks for the suggestions
Hardware gl seems to be fine, glxgears runs smoothly:
$ glxinfo | grep -i direct
direct rendering: Yes
I'll follow up with more details soon, but I doubt volume
of the
data is the problem, it's quite modest by PDL standards,
and when I'm using the "twiddle" mode to look-around an
unchanging model there is no flicker. Previously I just
had a mesh which seemed ok but when I used a filled sheet
there is a noticeable flicker as the light sheet is draw
over the dark background.
I might not need double-buffering exactly, but a GL
equivalent that only draws once all the things to draw
are queued.