// replace png with tiff if your PNG lib causes problems
// increase the number after -s for better resolution
scene set view=left
write l.png -s 1000
scene set view=right
write r.png -s 1000
scene set view=center
// the system command below uses montage from the ImageMagick package!
system montage +label +frame +shadow -geometry 100% -tile 2x1 l.png r.png stereo.png
system rm l.png r.png