Volume 06 (1987)
Permanent URI for this community
Browse
Browsing Volume 06 (1987) by Issue Date
Now showing 1 - 20 of 114
Results Per Page
Sort Options
Item ACM SIGGRAPH 86, Dallas, Texas, 18-22 August(Blackwell Publishing Ltd and the Eurographics Association, 1987) Robinson, K.Item An Editor for Constructing Graphics with TEX(Blackwell Publishing Ltd and the Eurographics Association, 1987) Waldschmidt, H.Item An Algorithm for 3D Scan-Conversion of Polygons(Eurographics Association, 1987) Kaufman, ArieA three-dimensional (3D) scan-conversion algorithm, that scanconverts 3D planar polygons into their discrete voxel-map representation within a Cubic Frame Buffer (CFB), is presented. The algorithm, which is a variation of a 2D scan-line filling algorithm, is incremental and uses only simple operations like additions and testy inside the inner loops. The algorithm performs scan-conversion with computational complexity which is linear in the number of voxels written to the CFB. The paper also presents an algorithm that scan-converts polygons clipped to the CFB boundaries with no added time complexity. An all-integer decision mechanism which makes the inner-most loop of the algorithm more efficient is discussed too. All the algorithms guarantee lack of 6-connected "tunnels" in the converted polygons. The algorithms have been implemented as part of the 3D geometry processor of the CUBE Architecture, which is a voxel-based system for 3D graphics. These algorithms allow the' CUBE system to generate the essential primitive polygon within the CFB from a 3D geometric model.Item Computer Graphics Metafile Open Systems Opportunity Study(Blackwell Publishing Ltd and the Eurographics Association, 1987)Item Doctoral Theses in Computer Graphics(Blackwell Publishing Ltd and the Eurographics Association, 1987)A Formal Description Method for User Interfaces, October 1986 by Lynn MarshalOn New Types of Solid Models and their Visualization with Ray Tracing by J.J. van WijkGeometric Mine Modeling: Modeling of Three Dimensional Objects Based on Incomplete Information, 1985 by Olli KaronenIntegration of Free-Form Surfaces and Solid Modelling, 1985 by Per-Olof FjaTlliustroTmItem Efficient and Consistent Algorithms for Determining the Containment of Points in Polygons and Polyhedra(Eurographics Association, 1987) Chen, Min; Townsend, TeeterAlgorithms are presented for the determination of whether a given point E2 in is interior to, exterior to or on an arbitrary polygonal boundary and for the determination of whether a point in E 3 is interior to, exterior to or on a simple polyhedral boundary. The algorithms are based on the principle of using binary coded coordinate systems and parity counting of the number of intersections of the polygon or polyhedron boundary with an infinite vector. The amount of floating-point arithmetic, including arithmetical and comparative operations has been reduced to a minimum making the algorithms very suitable for implementation in either low-level language software or by hardware. Performance of the algorithms is compared with a number of others taken from the literature and a considerable increase in efficiency is apparent. The algorithms are also shown to be consistent.Item New Methods for Improving the GKS Fill Area Output Primitive(Blackwell Publishing Ltd and the Eurographics Association, 1987) Herman, Ivan; Reviczky, JanosThe fill area primitive is one of the most powerful primitives of GKS and its derivatives (GKS-3D, PHIGS etc.). Since its specrfication is extremely general, it is important to explore new approaches to achieve higher performance in its implementation. In this paper fast algorithms are presented for special situations, which can be included, together with appropriate tests, into a complete GKS output pipeline. As a result, a speed improvement With a factor of two may be achieved in important practical cases.Item Graphical Analysis of Complex O.D.E. Solutions(Blackwell Publishing Ltd and the Eurographics Association, 1987) Richard, F.Item Extended Octtrees, between CSG Trees and Boundary Representations(Eurographics Association, 1987) Navazo, Isabel; Fontdecaba, Josep; Brunet, PereBesides the most widely used models in the Geometric Modeling Systems, Constructive Solid Geometry (CSG) and Boundary Representations (BR), Octtrees have appeared as an alternative representation scheme which is particularly well suited for the solid boolean operation algorithms. Extended Octtrees, which incorporates three additional node types containing part of the surface of the object, are much more compact and allow the exact representation of plane faced objects, while supporting also low complexity algorithms for boolean operations. Due to the limitations of the two main models, CSG and Boundary Representation , a number of Hybrid Systems have appeared, which support both schemes and perform every operation in the most suitable model. However, algorithms for the boundary evaluation of CSG trees are complex, and at the moment little is known on algorithms for the inverse conversion, from BR to CSG. In the present paper, the use of the Extended Octtree model as an intermediate tool in the conversions between. CSG trees and BR is studied. In the case of CSG trees build from primitives with plane faces, an algorithm for the conversion from the CSG model to the Extended Octtree representation is presented. Its complexity is linear with respect to the numbe of nodes in the Octtree. The use of this algorithm in model-to-model conversions is discussed, together with the BR to Extended Octtree and Extended Octtree to BR conversion algorithms, that present also linear complexity with respect to the total number of nodes.Item Offers to EUROGRAPHICS Members(Blackwell Publishing Ltd and the Eurographics Association, 1987)Item EUROGRAPHICS Membership Application Forms(Blackwell Publishing Ltd and the Eurographics Association, 1987)Item THE CGM - A METAFILE FOR GKS?(Blackwell Publishing Ltd and the Eurographics Association, 1987) Brodlie, Ken; Henderson, Lofton; Mumford, AnneItem EDITORIAL(Blackwell Publishing Ltd and the Eurographics Association, 1987) Arnold, DavidItem Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1987)Item An Automatic Interpolation Method of Grayvalued Images Utilizing Density Contour Lines(Eurographics Association, 1987) Agui, Takeshi; Saito, Minoru; Nakajima, Masayuki; Arai, YukihiroThis paper presents an automatic method of interpolation or inbetweening for gray valued images, which have been difficult to be processed automatically. The method consists of three parts. The first i s the extraction of density contour lines from a pair of gray valued key frame images, the second i s the interpolation of the contour lines and the l a s t is the generation of in-between gray valued images. In the second part, the correlation of corresponding contour lines of the key frames i s carried out automatically utilizing some kinds of similarity functions. The method is applied to a pair of pictures of a plaster head photographed slightly different directions and generates a very smooth rotating animation picture of the p l a s t e r head. This method has much applicability to computer animation and motion picture analysis. Stereo pair images are available from key frame pictures of objects photographed from any direction. Interpolation of color images is also possible.Item Conformal Texture Mapping(Eurographics Association, 1987) Fiume, E.; Fournier, A.; Canale, V.A new class of geometric mappings is introduced to computer graphics, and the utility of this class is illustrated by applying it to texture mapping. When mapping a texture onto a surface such as a polygon, the entire texture can rarely be mapped without some clipping or non-linear transformation. Is it possible to map a texture bijectively to an arbitrary polygon such that the entire texture is mapped? This paper presents a solution to this problem. A new class of mapping techniques based on conformal mapping is proposed. The technique allows one to construct a continuous, bijective map from a polygonal texture space (e.g., a square) to an arbitrary convex polygon. The resulting map is texture-independent. The theory and .an implementation of conformal texture mapping is discussed, and several simple filtering techniques to support it are outlined. Conformal mapping extends the range of geometric mapping techniques, and is pertinent to many areas of computer graphics. Other examples of the potential utility of conformal mappings are also discussed.Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1987)Item EDITORIAL(Blackwell Publishing Ltd and the Eurographics Association, 1987) Arnold, DavidItem Preserving the Area of Regions(Blackwell Publishing Ltd and the Eurographics Association, 1987) Williams, RichardWhen regions are represented by their boundary, the number of points ((x, y) coordinate pairs) used to define the boundary can vary. Many more points are required to satisfactorily display a region at a detailed scale than at a broad scale. The area of a region is an important property in geographic and other applications, and it can easily be computed from the sequence of points. However, reducing or increasing the number of points in the sequence will usually alter the area. This paper considers how the region s area could be preserved by approximation algorithms, which reduce the number of points, and by enhancement algorithms, which increase the number of points.Item EUROGRAPHICS 87(Blackwell Publishing Ltd and the Eurographics Association, 1987)