Making Things See

Accessing Joint Positions

When we last left draw, we’d successfully accessed our tracked user from the list of users provided by OpenNI, but skeleton data was not yet available, so we were not able to proceed. Now that we’ve finished calibrating our user, the tables have turned—kinect.isTrackingSkeleton(userId) will return true and we’ll be able to enter the inner if statement. From here on out, our job is to actually use the skeleton data provided by OpenNI to build an interface.

In this sketch, we’re going to create the simplest interface possible: a red dot that follows your right hand. Creating this interface will take three steps. First we have to get the position of the right hand from OpenNI. OpenNI will give us this position in “real-world” ...