I just found these download on the page of Shigeyuki Hirai, who does
the Max/MSP port of Gem. He has two interesting objects that
shouldn't be to hard to get working in Pd, since they are already Gem
objects.
http://www.cc.kyoto-su.ac.jp/~hirai/softwares/index-j.html
One is pix_qrencode which is based on libqrencode, which lets you
read those 2D barcodes.
The other is pix_artoolkit, which is based on ARToolkit, which is a
type of code to stick on things that you can then track in 3D space
using Gem.
Just throwing that out there in case anyone is interested.
.hc
Mistrust authority - promote decentralization. - the hacker ethic