A new method is presented of cell loss protection for packet video environments that uses scrambling and deinterleaving in conjunction with block transform coding of the video signal. The input video sequence is first...
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A new method is presented of cell loss protection for packet video environments that uses scrambling and deinterleaving in conjunction with block transform coding of the video signal. The input video sequence is first de-interleaved by separating the sequence into subsequences using a subsampling process. This allows better prediction of lost data when packets are lost. Each subsequence is then coded using the DCT, and the coded coefficients are packetized into cells in a pseudorandom, scrambled manner. Consequently, if several adjacent cells are lost, the loss of information will be spatially and spectrally random. Because of the random nature of the lost information, recovery from cell loss and concealment of the loss data by prediction from surrounding coefficients is greatly improved. The result is an improvement in perceptual quality over existing packetization methods when cells are lost.< >
The author presents a novel method for animating water based on a simple, rapid, and stable solution of a set of partial differential equations resulting from an approximation to the shallow water equations. The appro...
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The author presents a novel method for animating water based on a simple, rapid, and stable solution of a set of partial differential equations resulting from an approximation to the shallow water equations. The approximation gives rise to a version of the wave equation on a height field where the wave velocity is proportional to the square root of the depth of the water. The resulting wave equation is then solved with an alternating-direction implicit method on a uniform finite-difference grid. The computational work required for an iteration consists mainly of solving a simple tridiagonal linear system for each row and column of the height field. A single iteration per frame suffices in most cases for convincing animation. Unlike previous models, the proposed method handles wave reflections, net transport of water, and boundary conditions with changing topology.< >
Vanguard is an experimental OS-level framework for distributed applications. Vanguard consists of an object-oriented protocol suite and object model, a set of programming language interfaces that can be used to access...
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Vanguard is an experimental OS-level framework for distributed applications. Vanguard consists of an object-oriented protocol suite and object model, a set of programming language interfaces that can be used to access or implement Vanguard objects, and a modular, configurable kernel and implements object invocation. This paper outlines these three facets of Vanguard, focusing on the relationship between 'system' (Vanguard) objects and 'language' objects.< >
This paper advances a means by which the conventions and methods of digital "painting" and image manipulation programs can be extended into the third dimension, providing sculpting tools that are natural and...
ISBN:
(纸本)0897913515
This paper advances a means by which the conventions and methods of digital "painting" and image manipulation programs can be extended into the third dimension, providing sculpting tools that are natural and appropriate for a restricted but very useful class of models. Attempts to approximate "drawing" in 3D do not necessarily involve computer graphics [Gregory71]. Efforts in this area are a subject of continuing graphics research [Schmandt82], [Sachs89]. The key to the approach undertaken in the work described here is the use of an unusual hardware technique for displaying video rasters as surfaces. With such a display, existing software for 2D graphics and image processing can be used, without modification, for creating and modifying three-dimensional surfaces. The resulting raster data can then be converted into conventional 3D databases for further processing and display. The aim of this research is to create consistent, unified methods for computer-assisted drawing, painting, modeling, and animation.
Too few interface designers actually use an iterative design process. Too few interface designers actually involve their anticipated users throughout the design of an interface. In order to build better interfaces, we...
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Traditional radiosity methods can compute the illumination for a scene independent of the view position. However, if any part of the scene geometry is changed, the radiosity process will need to be repeated from scrat...
ISBN:
(纸本)9780897913447
Traditional radiosity methods can compute the illumination for a scene independent of the view position. However, if any part of the scene geometry is changed, the radiosity process will need to be repeated from scratch. Since the radiosity methods are generally expensive computationally, the traditional methods do not lend themselves to interactive uses where the geometry is constantly changing. This paper presents a new radiosity algorithm to incrementally render scenes with changing geometry and surface attributes. In other words, the question to be asked is "What is the minimum recomputation I need to do if I turn off a light source, change the color of a surface, add or move an object?" Because a modeling change generally exhibits some coherence and affects only parts of an image, the proposed method may drastically reduce the rendering time and therefore allow interactive manipulation. In addition, since the method is conducted incrementally and view-independently, the rendering process can start before the modeling process is completed. The traditional paradigm of modeling-then-rendering is changed to rendering-while-modeling. This approach not only gives the user better visual feedback but also effectively utilizes CPU time otherwise wasted in the modeling process.
An overview is given of Vanguard, an experimental object-oriented distributed operating system kernel currently under development. Vanguard is defined by a protocol suite and object model, independent of any particula...
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An overview is given of Vanguard, an experimental object-oriented distributed operating system kernel currently under development. Vanguard is defined by a protocol suite and object model, independent of any particular programming language. The Vanguard protocols and object model are implemented by a distributed kernel that is also structured as an object-oriented Vanguard application. Although object oriented, Vanguard is not based on any single programming language, object oriented or otherwise. The Vanguard kernel currently runs only as an application on top of existing host operating systems.< >
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