Animating an articulated figure usually requires expensive hardware in terms of motion capture equipment, processing power and rendering power. This implies a high cost system and thus eliminates the use of personal computers to drive avatars in virtual environments. We propose a system to animate an articulated human upper body in real-time, using minimal motion capture trackers to provide position and orientation for the limbs. The system has to drive an avatar in a virtual environment on a low-end computer. The cost of the motion capture equipment must be relatively low (hence the use of minimal trackers). We discuss the various types of motion capture equipment and decide to use electromagnetic trackers which are adequate for our requirements while being reasonably priced. We also discuss the use of inverse kinematics to solve for the articulated chains making up the topology of the articulated figure. Furthermore, we offer a method to describe articulated chains as well as a process to specify the reach of up to four link chains with various levels of redundancy for use in articulated figures. We then provide various types of constraints to reduce the redundancy of non-defined articulated chains, specifically for chains found in an articulated human upper body. Such methods include a way to solve for the redundancy in the orientation of the neck link, as well as three different methods to solve the redundancy of the articulated human arm. The first method involves eliminating a degree of freedom from the chain, thus reducing its redundancy. The second method calculates the elevation angle of the elbow position from the elevation angle of the hand. The third method determines the actual position of the elbow from an average of previous positions of the elbow according to the position and orientation of the hand. The previous positions of the elbow are captured during the calibration process. The redundancy of the neck is easily solved due to the small amount of redundancy in the chain. When solving the arm, the first method which should give a perfect result in theory, gives a poor result in practice due to the limitations of both the motion capture equipment and the design. The second method provides an adequate result for the position of the redundant elbow in most cases although fails in some cases. Still it benefits from a simple approach as well as very little need for calibration. The third method provides the most accurate method of the three for the position of the redundant elbow although it also fails in some cases. This method however requires a long calibration session for each user. The last two methods allow for the calibration data to be used in latter session, thus reducing considerably the calibration required. In combination with a virtual reality system, these processes allow for the real-time animation of an articulated figure to drive avatars in virtual environments or for low quality animation on a low-end computer.

Thesis (Masters Diploma (Electrical Engineering)--Cape Technikon, Cape Town, 1993 / This thesis describes the design and development of a computer vision system. The system (Video Frame Grabber) will give PCUsers the potential to capture any visual image into the memory of a computer. This computer intelligible image opens the way for new development in computer photography, Image recognition and . Desktop Publishing.

University of Macau / Faculty of Science and Technology / Department of Computer and Information Science

University of Macau / Faculty of Science and Technology / Department of Computer and Information Science

University of Macau / Faculty of Science and Technology / Department of Computer and Information Science

M.Sc. (Computer Science) / This dissertation examines the field of computer vision, with special attention being given to vision systems that support digitized video image analysis. The study may be broadly divided into three main sections. The first part offers an introduction to standard vision systems, focusing on the hardware architectures and the image analysis techniques used on them. Hardware configurations depend mainly on the selected frame-grabber and processor type. Parallel architectures are highlighted, as they represent the most suitable platform for a real-time digitized video image analysis system. The image analysis techniques discussed include: image preprocessing, segmentation, edge detection, optical flow analysis and optical character recognition. The second part of the study covers a number of real-world computer vision applications, and commercially available development environments. Several traffic surveillance systems are discussed in detail, as they relate to the practical vehicle identification system developed in the third part of the study. As mentioned above, the development of a Vehicle Identification Prototype, called VIP, forms the basis for the third and final part of this study. The VIP hardware requirements are given, and the software development and use is explained. The VIP's source code is provided so that it may be evaluated, or modified, by any interested parties.

M.Ing. (Electrical and Electronic Engineering) / Please refer to full text to view abstract

Landslides in the landscape exhibit predictable properties of shape, structure and orientation. These properties are reflected to varying degrees in their depiction in a satellite image. Landslides can be isolated along with similar objects in a digital image using differential and template operators. Extraction of the landslide features from these images can proceed using a logic-based model which draws on an appropriate object definition approximating the depiction of the landslides in an edge-operated image and a digital elevation model. An object extraction algorithm based on these concepts is used in repeated trials to ascertain the effectiveness of this automated approach. A low resolution linear object definition (Fischler et al. , 1981) is used to isolate candidate pixel segments in three enhanced images. These segments are classified as landslides or non-landslides according to their image pixel intensity, length, slope, and orientation. Digital elevation data is used to evaluate slope and orientation criteria. Results are compared to an inventory of landslides made using aerial photographs. Study results indicate that 17% to 28% of landslides in the image are identified for trials that produce a commission error rate of less than 50%. Commission errors are dominated by image objects related to roads and waste wood areas in clearcuts. A higher rate of successful identification was noted for landslides which occurred within 15 years of image acquisition (24% to 32%), and was most apparent for the subset of that group which was located in areas that were harvested more than 15 years before acquisition or were unharvested (29% to 38%). Successful identifications in the trials are dominated by events greater than 300 metres long and wider than 20 metres. The results suggest that the approach is more reliable in unharvested areas of the image. The poor quality of the digital elevation data, specifically artifacts produced by the contour-to-grid algorithm, was partly responsible for errors of commission and omission. The simplicity of the object definition used is another factor in error production. The methodology is not operational, but represents a realistic approach to scene segmentation for resource management given further refinement. / Forestry, Faculty of / Graduate

The problem of restoring an image distorted by a system consisting of a stochastic impulse response in conjuction with additive noise is investigated. The method of constrained least squares is extended to this problem, and leads to the development of a new technique based on the minimization of a weighted error function. Results obtained using the new method are compared with those obtained by constrained least squares, and by the Wiener filter and approximations thereof. It is found that the new technique, "Weighted Least Squares", gives superior results if the noise in the impulse response is comparable to or greater than the additive noise. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

One method of resolving the ambiguity inherent in interpreting images is to add different sources of information. The multiple information source paradigm emphasizes the ability to utilize knowledge gained from one source that may not be present in another. However, utilizing disparate information may create situations in which data from different sources are inconsistent. A schemata-based system has been developed that can take advantage of multiple sources of information. Schemata are combined into a semantic network via the relations decomposition, specialization, instance of, and neighbour. Control depends on the structure of the evolving network and a cycle of perception. Schemata cooperate by message passing so that attention can be directed where it will be most advantageous. This system has been implemented to interpret aerial photographs of small urban scenes. Geographic features are identified using up to three information sources: the intensity image, a sketch map, and information provided by the user. The product is a robust system where the accuracy of the results reflects the quality and amount of data provided. Images of several geographic locales are analyzed, and positive-results are reported. / Science, Faculty of / Computer Science, Department of / Graduate