An interesting class of two- and three-dimensional space structures can be derived from projections of higher-dimensional structures. Regular polygons and regular-faced polyhedra provide the geometry of families of n-...
An interesting class of two- and three-dimensional space structures can be derived from projections of higher-dimensional structures. Regular polygons and regular-faced polyhedra provide the geometry of families of n-stars from which two- and three-dimensional projections of n-dimensional grids can be derived. These projections are rhombic space grids composed of all-space filling rhombi and rhombohedra with edges parallel to n directions. An infinite class of single-, double- and multi-layered grids can be derived from n-sided polygons and prisms, and a finite class of multi-directional grids from the polyhedral symmetry groups. The grids can be periodic, centrally symmetric or non-periodic, and act as skeletons to generate corresponding classes of space-filling, packings and labyrinths.
The goal of science is to understand why things are the way they are. By emulating the logic of nature, computer simulation programs capture the essence of natural objects, thereby serving as a tool of science. When t...
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An automated method of synchronizing facial animation to recorded speech is described. In this method, a common speech synthesis method (linear prediction) is adapted to provide simple and accurate phoneme recognition...
ISBN:
(纸本)9780897912136
An automated method of synchronizing facial animation to recorded speech is described. In this method, a common speech synthesis method (linear prediction) is adapted to provide simple and accurate phoneme recognition. The recognized phonemes are then associated with mouth positions to provide keyframes for computer animation of speech using a parametric model of the human *** linear prediction software, once implemented, can also be used for speech resynthesis. The synthesis retains intelligibility and natural speech rhythm while achieving a “synthetic realism” consistent with computer animation. Speech synthesis also enables certain useful manipulations for the purpose of computer character animation.
One of the major problems in developing computeraided design software is the establishment of effective man-machine communication. This paper describes a computer-aided plate girder design software package and its man...
作者：
Jules BloomenthalXerox PARC
Palo Alto California and Computer Graphics Laboratory New York Institute of Technology Old Westbury New York
A method is presented for representing botanical trees, given three-dimensional points and connections. Limbs are modeled as generalized cylinders whose axes are space curves that interpolate the points. A free-form s...
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ISBN:
(纸本)9780897911665
A method is presented for representing botanical trees, given three-dimensional points and connections. Limbs are modeled as generalized cylinders whose axes are space curves that interpolate the points. A free-form surface connects branching limbs. "Blobby" techniques are used to model the tree trunk as a series of non-circular cross sections. Bark is simulated with a bump map digitized from real world bark; leaves are textures mapped onto simple surfaces.
In this paper a new method of representing topological information in 1, 2 and 3 dimensions is presented based on a ordered-adjacency relation amongst the different topological elements. This relation follows naturall...
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ISBN:
(纸本)0048014407
In this paper a new method of representing topological information in 1, 2 and 3 dimensions is presented based on a ordered-adjacency relation amongst the different topological elements. This relation follows naturally from considerations of adjacency, ordering and valency. Constraints are then derived which guarantee that models stored in the database are well-formed, that is, are orientable, closed manifolds. These constraints and other representation independent properties can be expressed using relational algebra.
This paper discusses some of the issues concerned with keyframed computer animation of 3-D articulated models and the problems in designing interactive systems for this type of animation. Examples are taken from the f...
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This paper discusses some of the issues concerned with keyframed computer animation of 3-D articulated models and the problems in designing interactive systems for this type of animation. Examples are taken from the four years of keyframe animation of articulated models done at the NYIT computergraphics Lab, and from our recent attempts to refine our original keyframe animation system, BBOP. 15 refs.
An algorithm is described that utilizes the spatial coherence of polygonal environments by combining features of both image and object space hidden surface algorithms. Instead of tracing infinitesimally thin rays of l...
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ISBN:
(纸本)0897911385
An algorithm is described that utilizes the spatial coherence of polygonal environments by combining features of both image and object space hidden surface algorithms. Instead of tracing infinitesimally thin rays of light, we sweep areas through a scene to form beams. This technique works particularly well for polygonal models since for this case the reflections are linear transformations, and refractions are often approximately so. The recursive beam tracer begins by sweeping the projection plane through the scene. Beam-surface intersections are computed using two-dimensional polygonal set operations and an occlusion algorithm similar to the Weiler-Atherton hidden surface algorithm. For each beam-polygon intersection the beam is fragmented and new beams created for the reflected and transmitted swaths of light. These sub-beams are redirected with a 4 multiplied by 4 matrix transformation and recursively traced. This beam tree is an object space representation of the entire picture.
Ray tracing has produced some of the most realistic computer generated pictures to date. They contain surface texturing, local shading, shadows, reflections and refractions. The major disadvantage of ray tracing resul...
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ISBN:
(纸本)9780897911382
Ray tracing has produced some of the most realistic computer generated pictures to date. They contain surface texturing, local shading, shadows, reflections and refractions. The major disadvantage of ray tracing results from its point-sampling approach. Because calculation proceeds ab initio at each pixel it is very CPU intensive and may contain noticeable aliasing artifacts. It is difficult to take advantage of spatial coherence because the shapes of reflections and refractions from curved surfaces are so *** this paper we describe an algorithm that utilizes the spatial coherence of polygonal environments by combining features of both image and object space hidden surface algorithms. Instead of tracing infinitesimally thin rays of light, we sweep areas through a scene to form “beams.” This technique works particularly well for polygonal models since for this case the reflections are linear transformations, and refractions are often approximately *** recursive beam tracer begins by sweeping the projection plane through the scene. Beam-surface intersections are computed using two-dimensional polygonal set operations and an occlusion algorithm similar to the Weiler-Atherton hidden surface algorithm. For each beam-polygon intersection the beam is fragmented and new beams created for the reflected and transmitted swaths of light. These sub-beams are redirected with a 4×4 matrix transformation and recursively traced. This beam tree is an object space representation of the entire *** the priority of polygons is pre-determined, the final picture with reflections, refractions, shadows, and hidden surface removal is easily drawn. The coherence information enables very fast scan conversion and high resolution output. Image space edge and texture antialiasing methods can be applied.
作者：
WATERMAN, SGORDON, DSTANLEY WATERMAN (Ph.D. in Geography
University of Dublin 1969) is Senior Lecturer in Geography at the University of Haifa Haifa 31999 Israel. He has research interests in political and social geography. DAN GORDON (D.Sc. in Mathematics
Technion—Israel Institute of Technology—1976) is Lecturer in Computer Studies at the University of Haifa. His research interests include design and analysis of algorithms VLSI computational geometry and computer graphics.
A quantitative procedure for analyzing and comparing distortion in mental maps is presented. Using a microcomputer and digitizer, and by developing a distortion index, comparisons are made by direct analysis of mental...
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A quantitative procedure for analyzing and comparing distortion in mental maps is presented. Using a microcomputer and digitizer, and by developing a distortion index, comparisons are made by direct analysis of mental maps. A case study of the mental maps of Israel of high school and university students showed a tendency to generalize shape to simple geometric forms, with foreshortening of north-south lines and exaggeration of east-west distances.
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