||Motion capture (mocap) have been available for more than two decades now. Traditionally it is mainly used for animation and biomechanical analysis. Now it's growing into the consumer sector, with game devices such as the EyeToy and Wii Remote opening the scene. This presentation will introduce the basic principles in an optical marker based motion capture system, and look back at an industrial mocap project carried out at Qualisys, Göteborg. In the project old calibration and tracker routines were replaced with new ones, which turned out to work better in most cases.