Virtual primitives for the representation of features and objects in a remote telepresence environment.

This thesis presents the development of a set of novel graphical tools Known as 'virtual primitives' that allow the user of a stereoscopic telepresence system to actively and intuitively model features in a remote environment. The virtual primitives provide visual feedback during the model creating process in the form of a dynamic wireframe of the primitive overlaid and registered with the real object. The operator can immediately see the effect of his decisions and if necessary make minor corrections to improve the fit of the primitive during its generation. Virtual primitives are a generic augmented reality (AR) tool and their applications extend past the modelling of a workspace for telerobot operation to other remote tasks such as visual inspection, surveying and collaborative design. An AR system has been developed and integrated with the existing Surrey Telepresence System. The graphical overlays are generated using virtual reality software and combined with the video images. To achieve a one-to-one correspondence between the real and virtual worlds the AR system is calibrated using a simple pinhole camera model and standard calibration algorithm. An average RMS registration error between the video and graphical images of less than one framegrabber pixel is achieved. An assessment of a virtual pointer confirms that this level of accuracy is acceptable for use with the virtual primitives. The concept of the virtual primitives has been evaluated in an experiment to model three test objects. The results show that using a virtual primitive was superior in accuracy and task completion time to using a pointer alone. Finally, a case study on the remote inspection of sewers demonstrates the advantages of virtual primitives in a real application. It confirms that the use of virtual primitives significantly reduces the subjective nature of the task, offers an increase in precision by an order of magnitude over conventional inspection methods, and provides additional useful data on the characteristics of the sewer features not previously available