共查询到19条相似文献,搜索用时 703 毫秒
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一种trimmedNURBS曲面的裁剪方法 总被引:5,自引:1,他引:4
所研究trimmed NURBS曲面的裁剪方法分三步完成裁剪算法。其主要特点是将所有trimmed NURBS曲面与裁剪轮廓面的交线都转为封闭环,从而可以统一的方式处理各类裁剪问题。实验结果表明,该算法可方便地解决目前一些曲面造型系统对已裁剪的内部和外部边界无法再裁剪等问题,亦可应用于一般形式的trimmed参数曲面的裁剪操作。 相似文献
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基于球面三角网格逼近的等距曲面逼近算法 总被引:2,自引:0,他引:2
给出了一种基于球面三角网格逼近的等距曲面逼近新算法。利用三角网格逼近基球面,然后计算此三角网格按中心沿在曲面扫凉而成空间区域的边界作为等距曲面的逼近。该算法计算简单,方便地解决了整体误差问题,而且所得到的逼近曲面是与原曲面同次数的NURBS曲面。 相似文献
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参数曲面与平面求交的一种新方法 总被引:2,自引:0,他引:2
本文提出了一种新的参数曲面与平面求交算法,基于平面的半空间性质,通过参数域平面的二向线性插值,将求交问题转化为一系列简单的离散、判断、比较、排序等运算,能较好的解决曲面片内的交线不连续和交线丢失问题,算法简便,可靠性好,计算精度高,在NC自动编程中具有广泛的应用场合。 相似文献
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本文重点研究二次椭圆曲面与平面相交,求交线实形的方法。该方法的关键在于给定的条件利用作辅助曲面耿定出交已知曲面所截得的新投影面投影成圆,以定出交线实形上的点。 相似文献
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S. H. Lo 《International journal for numerical methods in engineering》1995,38(6):943-954
A fully automatic general scheme is proposed to determine and analyse the intersections between two groups of surfaces composed of triangular facets. By carefully maintaining the spatial position of the lines of intersection in regenerating mesh locally around surface intersections, pieces of surfaces can be arbitrarily combined and merged. A great variety of objects can be easily created by selectively putting together different surface parts derived from surface intersections. The new algorithm is best applied in conjunction with an existing surface mesh generator to enhance its general capability in dealing with objects built from intersecting surfaces. In fact, it is a powerful surface mesh manipulator, and through the repeated use of the process, complex structures can be rapidly and accurately constructed. 相似文献
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S.H. Lo 《International journal for numerical methods in engineering》2013,93(11):1191-1215
A generic algorithm is proposed to merge arbitrary solid tetrahedral meshes automatically into one single valid finite element mesh. The intersection segments in the form of distinct nonoverlapping loops between the boundary surfaces of the given solid objects are determined by the robust neighbor tracing technique. Each intersected triangle on the boundary surface will be triangulated to incorporate the intersection segments onto the boundary surface of the objects. The tetrahedra on the boundary surface associated with the intersected triangular facets are each divided into as many tetrahedra as the number of subtriangles on the triangulated facet. There is a natural partition of the boundary surfaces of the solid objects by the intersection loops into a number of zones. Volumes of intersection can now be identified by collected bounding surfaces from the surface patches of the partition. Whereas mesh compatibility has already been established on the boundary of the solid objects, mesh compatibility has yet to be restored on the bounding surfaces of the regions of intersection. Tetrahedra intersected by the cut surfaces are removed, and new tetrahedra can be generated to fill the volumes bounded by the cut surfaces and the portion of cavity boundary connected to the cut surfaces to restore mesh compatibility at the cut surfaces. Upon restoring compatibility on the bounding surfaces of the regions of intersection, the objects are ready to be merged together as all regions of intersection can be detached freely from the objects. All operations, besides the determination of intersections structurally in the form of loops, are virtually topological, and no parameter and tolerance is needed in the entire merging process. Examples are presented to show the steps and the details of the mesh merging procedure. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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矩形管双焦点不对称翻领成型器曲面研究 总被引:2,自引:2,他引:0
研究了矩形管双焦点不对称翻领成型器领口交接曲线和曲面的形成,建立了矩形管双焦点不对称翻领成型器的肩曲面及其边界曲线的数学模型,给出了其高度与其它参数的关系式,为矩形管双焦点不对称翻领成型器的CAD/CAM提供了数学理论依据. 相似文献
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Juan R. Cebral Fernando E. Camelli Rainald Lhner 《International journal for numerical methods in engineering》2002,55(2):177-190
Several extensions and improvements to surface merging procedures based on the extraction of iso‐surfaces from a distance map defined on an adaptive background grid are presented. The main objective is to extend the application of these algorithms to surfaces with sharp edges and corners. In order to deal with objects of different length scales, the initial background grids are created using a Delaunay triangulation method and local voxelizations. A point enrichment technique that introduces points into the background grid along detected surface features such as ridges is used to ensure that these features are preserved in the final merged surface. The surface merging methodology is extended to include other Boolean operations between surface triangulations. The iso‐surface extraction algorithms are modified to obtain the correct iso‐surface for multi‐component objects. The procedures are demonstrated with various examples, ranging from simple geometrical entities to complex engineering applications. The present algorithms allow realistic modelling of a large number of complex engineering geometries using overlapping components defined discretely, i.e. via surface triangulations. This capability is very useful for grid generation starting from data originated in measurements or images. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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