It seems like a silly question to me, but I’ve been having difficulty figuring out what a fiducial is.  From what I’ve picked up, it seems like basically just a recognized object.  Any information is appreciated.

Fiducial symbols were originally used I think to guide robots when placing electronic components, they are seen on circuit boards so the robot can get it’s bearings.  They are a type of symbol which uses a contrast ration of sorts (depending upon the type) to gather information such as x/y and rotation.

I’m sure one of the Reactivision crew will be able to help out more though.

Hello,
well a fiducial a graphical symbol, which is known beforehand to the computer vision algorithm and therefore the only task for the computer vision system is to identify and locate the fiducial symbol in the image. this task can be much faster and more efficient than recognizing any arbitrary shape in the image.
practically speaking, a fiducial symbol is a sticker that needs to be attached to a physical object in order to make it visible to the computer vision algorithm.
In the case of reacTIVision we are using these fiducials (at the moment 180 different symbols), which allow us to retrieve the ID and precise position and rotation angle of any marked object.

http://reactable.iua.upf.edu/pics/reactivision02.png

best,
Martin.K

I also did some research trying to figure out what a fiducial was.

The word means something that is “taken as standard of reference” or “having the nature of a trust”.

I also stumbled upon a project where someone was creating their own generator program.
http://www.flickr.com/photos/toxi/sets/72157603673805139/
http://code.google.com/p/fidgen/

Yes the fidgen creates fiducials for use with reactivision. Martin’s post above is excellent and he’s one of the best people to answer this question

Maybe I have to add some more background information about the fiducial symbols we use in reacTIVision.
Conceptually these symbols are based on Enrico Costanza’s d-touch system, which was used for the very first prototype of the reacTable which I built during my research stay at Media Lab Europe. Back in Barcelona my colleague Ross Bencina had a look at the concept and tweaked it quite a bit, so it would fit more to the requirements of a real time musical instrument. The current reacTIVision fiducial symbols are the result of improvements of the precision of the position and angle detection, while reducing the overall footproint of the symbol.

Probably I should also add that the most common use of a fiducial symbol was to mark a certain point or object in the image with a simple crosshair marker, like the one used on crash test dummies or in robotics applications. Looking up wordnet for example, the word “fiducial” basically translates to “trust” and in our case it is used as a fixed standard of reference for comparison or measurement “a fiducial point”.

best,
Martin.K

I’m sure this is the wrong thread for this question, but how would you go about using fiducials in a multi touch setup? Would you have to use an additional webcam to recognize them, or could the IR camera be able to do that?