Generalized cylinders (GCs) are a popular representational tool in computer vision. In medical imaging, the curved axis GC is particularly applicable to a number of elongated physical structures such as vasculature, b...
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Generalized cylinders (GCs) are a popular representational tool in computer vision. In medical imaging, the curved axis GC is particularly applicable to a number of elongated physical structures such as vasculature, bone and bronchi. In many of these instances, it is necessary to recover curved-axis GCs with arbitrary cross-sections. It is also vital that these structures, once recovered, can be analyzed and visualized with off-the-shelf algorithms and software packages. Such tools are usually designed to operate on the domain of polynomial or rational surfaces. Unfortunately most extant, suitably versatile GC representations do not admit rational parameterizations. We develop an entirely rational B-spline representation for generalized cylinders with curved axes and arbitrary cross-section functions. We demonstrate how our representation can be used as a deformable model by extracting a rational GC from pre-segmented spinal data using a discrete dynamic surface fit.
Object dataflow is a popular approach used in parallel rendering. The data representing the 3D scene is statically distributed among processors and objects are fetched and cached only on demand. Most previous object d...
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Object dataflow is a popular approach used in parallel rendering. The data representing the 3D scene is statically distributed among processors and objects are fetched and cached only on demand. Most previous object dataflow methods were implemented on shared memory architectures and exploited spatial coherency to reduce hardware cache misses. We propose an efficient model for object dataflow parallel volume rendering on message passing machines. The algorithm is introduced and its ray storage mechanism is used to support latency hiding by postponing computation on inactive rays. Memory usage is optimized by letting objects migrate and replicate at different processors rather than the common static assignments. Our cache only memory approach uses a distributed directory scheme to trace the location of objects at other nodes. A mechanism to minimize network congestion was implemented which optimizes channel utilization. Unlike previous methods, our approach can benefit from temporal coherence and effectively minimizes communication costs during animation on limited bandwidth multiprocessing environments. We report results of the algorithm's implementation on several platforms like Cray T3D, Convex SPP and DEC alpha cluster of workstations (COWs), and achieved higher efficiency and scalability than existing algorithms.
The rapid increase in the complexity of systems demands newapproaches to design exploration and trade-off analysis. Thispaper presents an exploration environment that provides a uniformway to perform exploration at th...
ISBN:
(纸本)9780897919203
The rapid increase in the complexity of systems demands newapproaches to design exploration and trade-off analysis. Thispaper presents an exploration environment that provides a uniformway to perform exploration at the conceptual (pre-specification)stages of design. The environment encapsulates knowledge abouthow to perform estimations in different application domains, andseparates a designer from the mechanics of the estimation process.
The increasingly complex design of embedded systems creates the problems of specifying consistent and satisfiable rate constraints on process execution rates, checking them for consistency and satisfiability, computin...
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ISBN:
(纸本)9780818677861
The increasingly complex design of embedded systems creates the problems of specifying consistent and satisfiable rate constraints on process execution rates, checking them for consistency and satisfiability, computing process execution rates, and debugging rate constraint violations. The high complexity of these problems requires a complete and automated framework to help the designer in producing correct systems in shorter design time. We present such a framework and its implementation in a tool called Ratan. Experiments on large benchmarks show the suitability of the tool for an interactive debugging environment.
This article outlines the research of a multi-national team to develop a new travel aid to increase the independent mobility of blind and partially sighted people. The MoBIC travel aid (MoTA) consists of two inter-rel...
Modern web-based Scientific Visualization applications try to overcome common limitations imposed by limited internet bandwidth, server bottlenecks or network latency. A further aspect is the desire to gain platform i...
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Modern web-based Scientific Visualization applications try to overcome common limitations imposed by limited internet bandwidth, server bottlenecks or network latency. A further aspect is the desire to gain platform independence by solely using instruments which are platform independent by conception: the programming language Java, the Virtual Reality Modeling Language (VRML), or the 3D API *** present a prototype of a hybrid web-based Scientific Visualization system which makes use of the increasing computational power of modern desktop workstations and personal computers on the client side, and the superior performance provided by a powerful machine on the server side. In order to achieve high interaction rates and to balance computational load the user can dynamically assign selected tasks to his client or to the *** the scientific field of human modeling we have implemented a hybrid web-based toolkit for the modeling of human muscles and skin. Our application allows the on-line generation and manipulation of three-dimensional implicit muscle models in a heterogeneous network and it offers various parameters to adjust computation and response time versus rendering quality.
The implementation of an efficient automatic test generation scheme for black box testing is discussed. It uses checkpoint encoding and antirandom testing schemes. Checkpoint encoding converts test generation to a bin...
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The implementation of an efficient automatic test generation scheme for black box testing is discussed. It uses checkpoint encoding and antirandom testing schemes. Checkpoint encoding converts test generation to a binary problem. The checkpoints are selected as the boundary and illegal cases in addition to valid cases to probe the input space. Antirandom testing selects each test case such that it is as different as possible from all the previous tests. The implementation is illustrated using benchmark examples that have been used in the literature. Use of random testing both with checkpoint encoding and without is also reported. Comparison and evaluation of the effectiveness of these methods is also presented. Implications of the observations for larger software systems are noted. Overall, antirandom testing gives higher code coverage than encoding random testing, which gives higher code coverage than pure random testing.
Elmore delay has been extensively used for interconnect delay estimation because its simplicity of evaluation makes it appropriate for layout design. However, since Elmore delay does not take into account the effect o...
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Elmore delay has been extensively used for interconnect delay estimation because its simplicity of evaluation makes it appropriate for layout design. However, since Elmore delay does not take into account the effect of inductance, the discrepancy between actual delay and Elmore delay becomes significant for long RLC transmission lines, such as for MCM and PCB interconnects. We describe a simple two-pole based analytic delay model that estimates arbitrary threshold delays for RLC lines when the response is nonmonotone; our model is far more accurate than the Elmore model. We also describe an application of our model for controlling response undershoot/overshoot and for the reduction of interconnect delay through constraints on the moments.
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