This paper investigates the use of infra-red detection for the development of a motion tracking CAD input system. Currently, 3D models in CAD systems are manipulated on screen using either a mouse or specialist devices such as a space navigator. The use of infra-red detectors instead of a mouse will enable the CAD system to track the physical movements of an operator to manipulate the on screen model. The research will also investigate the degree of accuracy of the detection mechanism in 3D space using one or two infra red cameras. Trials have shown that it is possible to detect stationary points in 3D space with good accuracy using one detector and link these points to form a 3D object in the CAD system. Further results showing accuracy of detection for non stationary points in space will be analysed and presented.