The demand on virtual planning systems is increasing, in particular for technical pretentious surgical interventions such as intracranial endoscopy. In this paper, a new virtual system for neuroendoscopy is presented....
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The demand on virtual planning systems is increasing, in particular for technical pretentious surgical interventions such as intracranial endoscopy. In this paper, a new virtual system for neuroendoscopy is presented. The main purpose of this system is to provide support for the planning and training of neuroendoscopic interventions. The software is applied for virtual endoscopic visualization of three-dimensional magnetic resonance data sets, using a clinical magnetic resonance scanner. Rendering is performed on a Hewlett-Packard unix workstation. Virtual endoscopy provides a three-dimensional view of the cerebral ventricles with good visualization of anatomic details. The rendering system used allows the generation of fly-through sequences through the entire ventricular system in real-time. Navigation is controlled by mouse movements. The visualization of the computer generated intraventricular spaces is adapted to the characteristics of the optical endoscope. The presented virtual neuroendoscopy system is a promising tool for planning and training of neuroendoscopic procedures. It provides the ability to simulate these procedures based on the patient's individual anatomy, prior to surgery.
The coding by which chromosomes represent candidate solutions is a fundamental design choice in a genetic algorithm. This paper describes a novel coding of spanning trees in a genetic algorithm for the degree-constrai...
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CAVE/sup TM/ displays offer many advantages over other virtual reality (VR) displays, including a large, unencumbered viewing space. Unfortunately, the typical tracking subsystems used with CAVE/sup TM/ displays tethe...
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CAVE/sup TM/ displays offer many advantages over other virtual reality (VR) displays, including a large, unencumbered viewing space. Unfortunately, the typical tracking subsystems used with CAVE/sup TM/ displays tether the user and lessen this advantage. We have designed a simple, low-cost foot tracker that is wireless, leaving the user free to move. The tracker can be assembled for less than $200 US, and achieves an accuracy of /spl plusmn/10 cm at a 20-Hz sampling rate. We have tested the prototype with two applications: a visualization supporting close visual inspection, and a walkthrough of the campus. Although the tracking was convincing, it was clear that the tracker's limitations make it less than ideal for applications requiring precise visual inspection. However the freedom of motion allowed by the tracker was a compelling supplement to our campus walkthrough, allowing users to stroll and look around corners.
The construction of a C/sup 1/ piecewise bicubic Bezier surface that interpolates a set of data points and lies on the same side of a given plane as the data points is presented. The main tasks in this construction pr...
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The construction of a C/sup 1/ piecewise bicubic Bezier surface that interpolates a set of data points and lies on the same side of a given plane as the data points is presented. The main tasks in this construction process are the adjustment of the tangent vectors and the determination of the twist vectors at the data points. The tangent vectors are modified by decreasing their magnitudes. The twist vectors are first set by an energy minimization process and then filtered through a modification process to ensure the constructed surface lies on one side of the given plane. The technique for determining the twist vectors has an interpolation precision of cubic polynomials.
A method to scale a multi-surface object while holding the shape and size of specific features (trimming curves) unchanged is presented. The new method includes an earlier version for a one-NURBS-surface object as a s...
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ISBN:
(纸本)0769505627
A method to scale a multi-surface object while holding the shape and size of specific features (trimming curves) unchanged is presented. The new method includes an earlier version for a one-NURBS-surface object as a special case by considering more general objects and more general features. The constrained scaling process is attach-and-deform based. The new surface is constructed by attaching the original features to a scaled version of the given object. The attaching process requires several transformations and a deformation of the scaled object. The resulting object has the same features as the original object while reflecting the shape and curvature distribution of the scaled object. The presented approach maintains a NURBS representation for each component surface of the resulting object and hence, is compatible with most of the current data-exchange standards. Test results on several car body surfaces with trimming curves are included. The quality of the resulting surfaces is examined using the highlight line model.
Let A and B be two convex polytopes in R3 with m and n facets, respectively. The penetration depth of A and B, denoted as π(A, B), is the minimum distance by which A has to be translated so that A and B do not inters...
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Modern dynamically scheduled processors use branch prediction hardware to speculatively fetch and execute most likely executed paths in a program. Complex branch predictors have been proposed which attempt to identify...
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Modern dynamically scheduled processors use branch prediction hardware to speculatively fetch and execute most likely executed paths in a program. Complex branch predictors have been proposed which attempt to identify these paths accurately such that the hardware can benefit from out-of-order (OOO) execution. Recent studies have shown that inspite of such complex prediction schemes, there still exist many frequently executed branches which are difficult to predict. Predicated execution has been proposed as an alternative technique to eliminate some of these branches in various forms ranging from a restrictive support to a full-blown support. We call the restrictive form of predicated execution as guarded execution. In this paper, we propose a new algorithm which uses profiling and selectively performs if-conversion for architectures with guarded execution support. Branch profiling is used to gather the taken, non-taken and misprediction counts for every branch. This combined with block profiling is used to select paths which suffer from heavy mispredictions and are profitable to if-convert. Effects of three different selection criterias, namely size-based, predictability-based and profiled-based on net cycle improvements, branch mispredictions and mis-speculated instructions are then studied. We also explain numerous adjustments that were made to the selection criterias to better reflect the OOO processor behaviour.
Gating is a very important technique of data association. Creating an excellent gate algorithm, which could efficiently decrease the number of extraneous returns falling within the gate, can improve the data associati...
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Gating is a very important technique of data association. Creating an excellent gate algorithm, which could efficiently decrease the number of extraneous returns falling within the gate, can improve the data association accuracy and decrease the computation complexity. Hence, a novel tracking gate algorithm is presented. The main feature of our method is to estimate the size of gate by calculating the optimal solution of an appraising function of the performance of the data association algorithm. A comparison of our method to classical methods demonstrates that our algorithm is superior to these methods, especially in a heavy clutter and false alarm environment.
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