The Luke hand contact sensor data returned from hx_update or hx_read_sensors don't seem to be mapped correctly according to the documentation, e.g., forces applied to the thumb are read on the index finger channel. I am not sure if this is a MuJoCo issue or a problem with the Luke hand model.
Are you looking at the latest documentation on the DEKA server, showing a table with 11 touch sensors? Are you taking into account the 0-based indexing? Are you using a LukeHand model that has 11 touch sensors defined at the and of the XML, namely: <touch site="palmFront" /> <touch site="palmBack" /> <touch site="palmInside" /> <touch site="palmOutside"/> <touch site="thumb" /> <touch site="thumbSide" /> <touch site="index" /> <touch site="indexSide" /> <touch site="middle" /> <touch site="ring" /> <touch site="little" />
Aha! We were referencing an out-of-date version of the documentation. This mapping makes much more sense.