EG1987 Proceedings (Technical Papers)
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Item COLOUR SECTION(Eurographics Association, 1987) -Item Active-Ray Tracing for 3D Medical Imaging(Eurographics Association, 1987) Trousset, Yves; Schmitt, FrancisLarge quantities of three-dimensional (3D) information are produced by 3D medical imaging techniques such as CT and MRI, in the form of digital volumes (DV). We propose a new approach to help a human observer to visualize these volumes. This approach is based on the idea that, in order to achieve true user-interaction, segmentation and visualization should not be treated separately. This is achieved by introducing active ray tracing, a method inspired by ray tracing but working directely on unsegmented digital volumes. Segmentation takes place as the active rays penetrate through the volume.Item Extraction and Organization of Form Features into a Structured Boundary Model(Eurographics Association, 1987) Falcidieno, Bianca; Giannini, FrancaA method is presented for the automatic identification and extraction of feature information from the solid model of an object. The procedure consists of recognizing shape features, extracting those features as solid volumes and arranging them in a hierarchical structure. In this hierarchical model the main shape of the object is represented at the highest levels of abstraction, while form features are described at lower levels of specification. The system is divided into three modules: feature recognition, feature extraction and feature organization. The recognition step works on a face-based representation of solid objects, called Face Adjacency Hypergraph [1] and it takes advantage of the Kyprianou's method [12]. In the extraction phase every recognized form feature is completed with dummy entities to form a feasible object and in the organization step the completed features are arranged in a hierarchical graph, called Structured Face Adjacency Hypergraph, which is a modification of a model defined in a previous work [1].Item Real-Time Scan-Line In-Fill(Eurographics Association, 1987) Allerton, D. J.; Evemy, J. D.; Zaluska, E. J.A novel algorithm is described to perform in-fill of wire-frame polygons, typically for application in visual systems for flight simulation. Post-processing is performed on an image formed in a conventional raster-scan framestore using edge-detection in scan-line order. A prototype real-time implementation of this algorithm is operational and is also presented.Item Unifying Vector and Polygon Algorithms for Scan Conversion and Clipping(Eurographics Association, 1987) Kilgour, AIistairIn both scan conversion and clipping, algorithm for dealing with polygons are generally presented independently of those for vectors, although many of the operations performed are similar. This paper shows how polygon algorithms for both problems can be developed from the corresponding vector algorithm. As well as yielding a unification at the conceptual level, this approach can lead to reduced code size in graphics system implementation, and produces polygon algorithms which are comparable in both robustness and efficiency with those previously presented.