共查询到18条相似文献,搜索用时 109 毫秒
1.
2.
本文探索NURBS曲面求交及构造过渡曲面的方法。基于交线跟踪算法求出NURBS曲面间的交线,算法比较稳定、可靠;采用参数化平面与等距面求交找出两曲面空间等距点,具有自然与变半径过渡曲面的定义相呼应、找点快、准确、稳定的特点;过渡曲面表示为2×3次NURBS曲面,自然、充分地利用了NURBS曲线可精确表示圆弧段的特性,过渡曲面具有表达简单、比较准确、便于采用统一的NURBS曲面处理算法对其进行各种几何处理的优点;实验证明这些方法可行,效果令人满意。 相似文献
3.
4.
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
5.
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
6.
基于Trimmed NURBS曲面几何特征的数字化自适应采样 总被引:3,自引:0,他引:3
曲面轮廓度误差评价和多边域逼近均要求对理论曲面进行数字化自适应采样。在对当前曲面数字化方法分析的基础上,针对Trimmed NURBS曲面,研究了在给定精度下的曲面数字化自适应采样方法,给出了基于曲率特征函数的曲线自适应采样和NURBS曲面多边域离散算法,提出了一种对大规模曲面网格点检测路戏优化问题很有效的进化算法一蚁群算法,并进行了计算机仿真实验验证。仿真结果表明,所提出的规划方法可显著提高数字化采样效率,具有很大的实用价值。 相似文献
7.
以往的曲面切割区域自动搜索算法通常以一般的曲面切割应用领域为基础,对于特殊产品设计领域,如服装设计、布绒玩具设计中的桥边和省道没有作必要的处理。因此,在基域搜索和切割过程中,对作为特殊切割线的桥边和省道提出了新的处理方法:通过复制桥边、省道与基域三角形曲面片的交点,在基域切割过程中利用同一三角形内同一线段上交点的连续性来区分原线段上的交点和复制交点,最终完成对基域的切割。与现有的算法相比,本算法对曲面切割线中的桥边和省道搜索更加智能,适合特殊、复杂的服装和玩具等产品设计领域。算法只对基域上的几何元素作了相应的处理,因而有着很高的效率。 相似文献
8.
以NURBS为数学模型,对曲面造型及加工系统进行了研究。在对各种算法分析、研究和改进的基础上,完成了一个集CAD/CAM于一体具有多种功能的曲面造型及加工系统,合理地将NURBS的主要核心配套技术和各种算法运用于NURBS造型系统中,通过交互方式成功实现了对多种曲线曲面(直线、圆弧、二次曲线、自由曲线、平面、二次曲面、旋转面、直纹面、雕塑曲面、截线面曲面、自由曲面、复杂组合曲面等)的造型生成。 相似文献
9.
10.
复合三角Bezier曲面/平面的过渡和裁剪 总被引:1,自引:0,他引:1
由初始交点出发,利用拓扑关系跟踪计算复合三角Bezier曲面与平面的交线,对一系列交点进行点对应修正,曲面片间边界点计算、交线两端交点的跟踪、截面线构造、截面线离散,构造出与基曲面达到G′连续、结构相似的过渡曲面,交点作为型值点值入复合曲面的型值点集中、对三角网格局域三角化,以交线为界分离,重新构造拓扑关系生成两张新的曲面,实现裁剪的目的,测试显示,上述方法简单可靠。 相似文献
11.
12.
A reconstruction approach is proposed based on a laser plane derived from the Random Sample Consensus (RANSAC) and three dimensional (3D) reference. The Hessian matrix is performed to extract the center points of the two intersection lines between the laser plane and the reference. The initial laser points are divided into two parts: the inner and exterior points. The inner points are chosen by the RANSAC method to fit the laser line, which avoids the interference of the exterior points. The intersection lines between the laser plane and the reference are represented by Plücker matrices. The laser plane is modeled by the intersection laser lines in the coordinate system of the reference and solved by the singular value decomposition method. The cylinders with known radii are employed to evaluate the accuracy of the laser plane, by comparing the reconstructed radii with the real values of the cylinders. The effects of the Gaussian noise, the distance from the camera to the 3D reference and the cylinder radius are investigated in the experiments. The average reconstruction errors of the three methods of RANSAC, Hough and least squares are 0.68, 1.47 and 2.32 mm in the four groups of experiments, respectively. The experimental results show that reconstruction method using the laser plane generated from the RANSAC and the 3D reference is reliable to present a high accuracy reconstruction for the vision reconstruction system. 相似文献
13.
采用"结式法"的圆环面和球面求交算法 总被引:1,自引:0,他引:1
提出了一种不需跟踪的求交算法.通过坐标变换使圆环中心轴与球心共处在XOZ平面内,然后讨论该平面内圆环面小圆和球面截圆的位置关系,给出了圆环面和球面不相交、交线为一个或两个圆、有孤立交点的几何条件以及交线的区间.最后,将圆环面和球面求交转化为平行于XOY面的平面内的两圆交点的问题并利用"结式法"解得交点. 相似文献
14.
A practical method for a noncontacting and real-time feature extraction for personal authentication is proposed. The finger geometry and feature extraction of the palmar flexion creases are integrated into a small number of discrete points based on the anatomical observation. For a video image of either palm, a palm placed freely facing toward a video camera is acquired. The fingers are brought together, and the palm is straightened out to eliminate any constraints. The discrete feature points for the fingers involve intersection points of the three finger (digital) flexion creases on the four finger skeletal lines. The feature points for the palm involve intersection points of the major palmar flexion creases and/or prominent creases of the palm on the extended finger skeletal lines. The orientations of the creases at the intersection points are also extracted features to be matched. The matching results are perfect for about 500 palm samples from 50 subjects so far. This discrete point processing, requiring no time-consumptive palmprint image analysis and requiring less than one second processing time, will contribute to a noncontacting, real-time and reliable feature extraction, easily combinable with other traits, for the personal authentication. 相似文献
15.
16.
Luiz Cristovo G. Coelho Marcelo Gattass Luiz Henrique de Figueiredo 《International journal for numerical methods in engineering》2000,47(4):777-800
We present an algorithm for intersecting finite element meshes defined on parametric surface patches. The intersection curves are modelled precisely and both meshes are adjusted to the newly formed borders, without unwanted reparametrizations. The algorithm is part of an interactive shell modelling program that has been used in the design of large offshore oil structures. To achieve good interactive response, we represent meshes with a topological data structure that stores its entities in spatial indexing trees instead of linear lists. These trees speed up the intersection computations required to determine points of the trimming curves; moreover, when combined with the topological information, they allow remeshing using only local queries. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
17.