Quartic Beta-splines have third-degree arc-length or geometric continuity at simple knots and are determined by three β or shape parameters. We present a general explicit formula for quartic Beta-splines, and determi...
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Quartic Beta-splines have third-degree arc-length or geometric continuity at simple knots and are determined by three β or shape parameters. We present a general explicit formula for quartic Beta-splines, and determine and illustrate the effects of varying the β parameters on the shape of a quartic Beta-spline curve. We show that quartic (and higher degree) rational Beta-splines with arc-length continuity satisfy the same continuity conditions as (nonrational) Beta-splines. We also show that the torsion continuous spline curves presented by Boehm ("Smooth Curves and Surfaces.” In Geometric Modeling: Algorithms and New Trends, G. E. Farin, Ed. SIAM, Philadelphia, Pa., 1987, pp. 175-184.) are equivalent to nonrational quartic Beta-spline curves, and determine the relationship between the shape parameters for the two types of curves. Finally, we present an algorithm for inserting a new knot and determining the refined control polygon.
We describe an approach to register and merge detailed facade models with a complementary airborne model. The airborne modeling process provides a half-meter resolution model with a bird's-eye view of the entire a...
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We describe an approach to register and merge detailed facade models with a complementary airborne model. The airborne modeling process provides a half-meter resolution model with a bird's-eye view of the entire area, containing terrain profile and building tops. The ground-based modeling process results in a detailed model of the building facades. Using the DSM obtained from airborne laser scans, we localize the acquisition vehicle and register the ground-based facades to the airborne model by means of Monte Carlo localization (MCL). We merge the two models with different resolutions to obtain a 3D model.
In this paper two subset line properties are introduced; the difference concerns the domain of the end points of the line segments under consideration, viz. Q 2 and Z 2 respectively. For both properties, a recursive a...
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In this paper two subset line properties are introduced; the difference concerns the domain of the end points of the line segments under consideration, viz. Q 2 and Z 2 respectively. For both properties, a recursive and a nonrecursive algorithm to generate raster line segments are derived. All algorithms use integer arithmetic only. The accuracy of the algorithms in representing lines will be discussed, as well as their time complexity.
New modifications of the Cohen-Sutherland algorithm for clipping lines and line segments in E-2 are presented. The suggested algorithms are based on a technique of coding the line direction together with the end point...
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New modifications of the Cohen-Sutherland algorithm for clipping lines and line segments in E-2 are presented. The suggested algorithms are based on a technique of coding the line direction together with the end points of the clipped line segment. They solve all cases more effectively. The algorithms are convenient for clippings lines or line segments by rectangle. Theoretical considerations and experimental results are also presented.
This paper presents a software development for the obtaining in an automatic way of three-dimensional models of objects (e.g. sculptures, mechanical pieces). Nowadays, there is available software which is able to crea...
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This paper presents a software development for the obtaining in an automatic way of three-dimensional models of objects (e.g. sculptures, mechanical pieces). Nowadays, there is available software which is able to create three-dimensional models of objects using laser systems, but they are pretty expensive (up to 120,000 Euro) due to the high technology used for data capture (laser scanner). On the other hand, the software depicted in this paper develops a new process that captures the data with a simple digital video camera and a motorized pedestal (about 1200 Euro). This way, more than 1300 images of the object are obtained. The later analysis of the edges of all these images will completely define the geometry of the object. So, this software is able to create accurate digital models with a resolution that varies from hundreds to one million of points. In order to export these three-dimensional models the software generates VRML, or ASCII files. These models are very useful in sciences like computer graphics, architecture, mechanics, automated mapping/facilities management, etc. (c) 2005 Elsevier Ltd. All rights reserved.
A VR-based simulator helps trainees develop skills for catheterization, a fundamental but difficult procedure in vascular interventional radiology. A deformable model simulates the complicated behavior of guide wires ...
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A VR-based simulator helps trainees develop skills for catheterization, a fundamental but difficult procedure in vascular interventional radiology. A deformable model simulates the complicated behavior of guide wires and catheters, using the principle of minimum total potential energy. A fast, stable multigrid solver ensures realistic simulation and real-time interaction. In addition, the system employs geometrically and topologically accurate vascular models based on improved parallel-transport frames, and it implements efficient collision detection. Experiments evaluated the method's stability, the solver's execution time, how well the simulation preserved the catheter's curved tip, and the catheter deformation's realism. An empirical study based on a typical selective-catheterization procedure assessed the system's feasibility and effectiveness.
We present a new technique to display a scene of three-dimensional isothetic parallelepipeds (3D-rectangles), viewed from infinity along one of the coordinate axes (axial view). In this situation, there always exists ...
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We present a new technique to display a scene of three-dimensional isothetic parallelepipeds (3D-rectangles), viewed from infinity along one of the coordinate axes (axial view). In this situation, there always exists a topological sorting of the 3D-rectangles based on the relation of occlusion (a dominance relation). The arising total order is used to generate the axial view, where the two-dimensional view of each 3D-rectangle is incrementally added, starting from the closest 3D-rectangle. The proposed scene-sensitive algorithm runs in time O(N log2N + d log N), where N is the number of 3D-rectangles and d is the number of edges of the display. This improves over the previously best known technique based on the same approach.
In the context of using virtual environments (VEs) in Internet-based teleoperation, this paper addresses the issue of parameter acquisition for single-image-based modeling of VEs. By studying the properties of basic t...
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In the context of using virtual environments (VEs) in Internet-based teleoperation, this paper addresses the issue of parameter acquisition for single-image-based modeling of VEs. By studying the properties of basic three-dimensional features such as point sets and edge corners, a parameter-searching method was developed that employs virtual objects as feature-matching templates. This approach is particularly valuable if the environment is subject to unpredictable change.
We present an algebraic algorithm to generate the exact general sweep boundary of a 2D curved object which changes its shape dynamically while moving along a parametric curve trajectory.
We present an algebraic algorithm to generate the exact general sweep boundary of a 2D curved object which changes its shape dynamically while moving along a parametric curve trajectory.
In this paper we present an efficient method for supporting image based lighting (IBL) for bidirectional methods. This improves both sampling of the environment, and the detection and sampling of important regions of ...
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In this paper we present an efficient method for supporting image based lighting (IBL) for bidirectional methods. This improves both sampling of the environment, and the detection and sampling of important regions of the scene, such as windows and doors. These parts of the scene often have a small area proportional to that of the entire scene, so paths which pass through them are generated with a low probability. The method proposed in this paper improves sampling efficiency, by taking into account view importance, and modifies the lighting distribution to use light transport information from the camera. This method automatically constructs a sampling distribution in locations which are relevant to the camera position, thereby improving sampling of light paths. This approach can be applied to several bidirectional rendering methods, and results are shown for bidirectional path tracing, metropolis light transport and progressive photon mapping. When compared to other methods, efficiency results demonstrate speed ups of orders of magnitude.
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