Conceptual design study for an advanced cab and visual system, volume 2

The performance, design, construction and testing requirements are defined for developing an advanced cab and visual system. The rotorcraft system integration simulator is composed of the advanced cab and visual system and the rotorcraft system motion generator, and is part of an existing simulation facility. User's applications for the simulator include rotorcraft design development, product improvement, threat assessment, and accident investigation

A parametric-space-based scan-line algorithm for rendering of bicubic surfaces

A novel scan-line algorithm for displaying bicubic surfaces is presented. Patches are decomposed on regions of constant sign of the z component of the normal before the scan process. Most of the computations are done in parametric space. The algorithm computes the intersection of the surfaces with only a restricted subset of scan planes and obtains the intersection with other scan planes by linear interpolation between exact intersections. A bound of the algorithm's error is given. The method is compared with Whitted's algorithm.Postprint (published version

Doctor of Philosophy

dissertationMany algorithms have been developed for synthesizing shaded images of three dimensional objects modeled by computer. In spite of widely differing approaches the current state of the art algorithms are surprisingly similar with respect to the richness of the scenes they can process. One attribute these algorithms have in common is the use of a conventional passive data base to represent the objects being modeled. This paper postulates and explores the use of an alternative modeling technique which uses procedures to represent the objects being modeled. The properties and structure of such "procedure models" are investigated and an algorithm based on them is presented

P-Buffer: Hidden-line rendering with a dynamic p-buffer

Despite the emergence of highly realistic computer-generated images, line-drawing images are still a common practice in showing the shapes and movements of three-dimensional objects. It is especially true when rendering time is critical in interactive applications such as the modeling and testing stage of computer aided design/manufacturing, computer animation, and virtual reality. Hence much effort has been devoted to provide sufficient information of the displayed objects with the least amount of time. While the techniques that determine visible surfaces in an image-space have the advantages on rendering speed and processable shapes, those that decide visible lines or line segments in an object-space are more suitable for showing hidden lines. The P-buffer algorithm introduced in this paper is a method for rendering line-drawing images with dashed hidden-lines. Being an image-space method, this algorithm preserves the low computational cost and works on a wide range of object shapes; as an extension to the Z-buffer algorithm it, moreover, discloses hidden surfaces by showing them with dashed lines. After a discussion on rendering techniques of line-drawing images, this paper presents this algorithm with pseudocode in C++ programming language and shows some experimental results as well. This image-space algorithm can be used as a compromise approach that reveals the concealed information of hidden-surface-removed views for time-critical rendering

Index based triangulation method for efficient generation of large three-dimensional ultrasonic C-scans

The demand for high speed ultrasonic scanning of large and complex components is driven by a desire to reduce production bottlenecks during the non-destructive evaluation of critical parts. Emerging systems (including robotic inspection) allow the collection of large data volumes in short time spans, compared to existing inspection systems. To maximize throughput, it is crucial that the reconstructed inspection data sets are generated and evaluated rapidly without a loss of detail. This requires new data visualization and analysis tools capable of mapping complex geometries whilst guaranteeing full part coverage. This paper presents an entirely new approach for the visualization of three-dimensional ultrasonic C-scans, suitable for application to high data throughput ultrasonic phased array inspection of large and complex parts. Existing reconstruction approaches are discussed and compared with the new Index Based Triangulation (IBT) method presented. The IBT method produces 3D C-scan representation, presented as coloured tessellated surfaces, and the approach is shown to work efficiently even on challenging geometry. An additional differentiating characteristic of the IBT method is that it allows easy detection of lack of coverage (an essential feature to ensure that inspection coverage can be guaranteed on critical components). Results demonstrate that the IBT C-scan generation approach runs over 60 times faster than a C-scan display based on Delaunay triangulation and over 500 times faster than surface reconstruction C-scans. In summary the main benefits of the new IBT technique are: • High speed generation of C-scans on large ultrasonic data sets (orders of magnitude improvement over surface reconstruction C-Scans) • Ability to operate efficiently on 3D mapped data sets (allowing 3D interpretation of C scans on complex geometry components) • Intrinsic indication of lack of inspection coverag

Tele-Autonomous control involving contact

Object localization and its application in tele-autonomous systems are studied. Two object localization algorithms are presented together with the methods of extracting several important types of object features. The first algorithm is based on line-segment to line-segment matching. Line range sensors are used to extract line-segment features from an object. The extracted features are matched to corresponding model features to compute the location of the object. The inputs of the second algorithm are not limited only to the line features. Featured points (point to point matching) and featured unit direction vectors (vector to vector matching) can also be used as the inputs of the algorithm, and there is no upper limit on the number of the features inputed. The algorithm will allow the use of redundant features to find a better solution. The algorithm uses dual number quaternions to represent the position and orientation of an object and uses the least squares optimization method to find an optimal solution for the object's location. The advantage of using this representation is that the method solves for the location estimation by minimizing a single cost function associated with the sum of the orientation and position errors and thus has a better performance on the estimation, both in accuracy and speed, than that of other similar algorithms. The difficulties when the operator is controlling a remote robot to perform manipulation tasks are also discussed. The main problems facing the operator are time delays on the signal transmission and the uncertainties of the remote environment. How object localization techniques can be used together with other techniques such as predictor display and time desynchronization to help to overcome these difficulties are then discussed

Interactive computation of radiation view factors

The development of a pair of computer programs to calculate the radiation exchange view factors is described. The surface generation program is based upon current graphics capabilities and includes special provisions which are unique to the radiation problem. The calculational program uses a combination of contour and double area integration to permit consideration of radiation with obstruction surfaces. Examples of the surface generation and the calculation are given

Robust point correspondence applied to two and three-dimensional image registration

Accurate and robust correspondence calculations are very important in many medical and biological applications. Often, the correspondence calculation forms part of a rigid registration algorithm, but accurate correspondences are especially important for elastic registration algorithms and for quantifying changes over time. In this paper, a new correspondence calculation algorithm, CSM (correspondence by sensitivity to movement), is described. A robust corresponding point is calculated by determining the sensitivity of a correspondence to movement of the point being matched. If the correspondence is reliable, a perturbation in the position of this point should not result in a large movement of the correspondence. A measure of reliability is also calculated. This correspondence calculation method is independent of the registration transformation and has been incorporated into both a 2D elastic registration algorithm for warping serial sections and a 3D rigid registration algorithm for registering pre and postoperative facial range scans. These applications use different methods for calculating the registration transformation and accurate rigid and elastic alignment of images has been achieved with the CSM method. It is expected that this method will be applicable to many different applications and that good results would be achieved if it were to be inserted into other methods for calculating a registration transformation from correspondence

The aliasing problem in computer-synthesized shaded images

Journal ArticleThis paper describes work toward improving the quality of computer-synthesized shaded images. Current (practical) hidden-surface algorithms produce an image whose precision is strictly limited by the number of picture elements. Problems caused by this limitation are described and explained in the text. Other image production media such as television and screen printing processes exhibit the same problems, but to a far lesser extent. Therefore, current image production media are surveyed and compared to computer-synthesized images with a view toward establishing a criterion for acceptable image quality