[Jcparkyn] clearly had an interesting topic for their thesis project, and was conscientious enough to write up a chunk of it and release it to the wild. The project in question is a digital pen that uses some neat sensor fusion to combine the inputs from a pen-mounted gyro/accelerometer with data from an optical tracking system provided by an off-the-shelf webcam.
This is a companion discussion topic for the original entry at https://hackaday.com/2023/11/14/d-point-a-digital-pen-with-optical-inertial-tracking/