首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 156 毫秒
1.
在地质模型中.曲面一般用三角网格来表示.在三维地质建模过程中经常需要对曲面进行裁剪操作,本文描述了一种网格曲面裁剪算法.它是将传统裁剪算法中的曲面三角网格和三角网格求交简化为曲面三角网格和矩形网格求交,由于矩形网格的数据结构简单.查找和定位方便(可以直接根据坐标值定位到所位于的矩形网格单元),算法简练,较大的提高了计算速度.  相似文献   

2.
本文综合网格逼近法和追踪法求交的优点,提出了一种曲面求交算法。该算法首先对曲面进行三角形网格划分,再用追踪法求各网格之间的交线,最后拟合成三次参数曲线。  相似文献   

3.
基于平均单元格的三角网格曲面快速求交算法   总被引:1,自引:0,他引:1       下载免费PDF全文
蒋钱平  唐杰  袁春风 《计算机工程》2008,34(21):172-174
在地质建模中,当待处理的曲面包含大量三角形时,求交速度成为了瓶颈。该文提出基于平均单元格的三角网格曲面快速求交算法,采用平均单元格技术对求交曲面进行预处理,以加快相交元素对的获取。实验结果表明,与同类求交算法相比,该算法能够有效提升求交速度,并已成功应用于某地质建模软件中。  相似文献   

4.
主要针对三角网格的细分曲面求交提出了一种有效的交线计算的方法,该方法适用于任意三角网格的细分曲面中.在利用AABB和二部图进行初始控制网格相交性检测后,利用该方法快速有效地求出细分曲面的交线.  相似文献   

5.
汪国华  于俊清  廖兆存 《计算机应用》2006,26(12):2884-2886
提出了显式方程和参数方程表示的曲面的一种绘制算法,该算法可以绘制任意复杂的方程曲面。首先将方程曲面离散成四边形网格,然后采用消隐算法消除曲面的自隐藏线。消隐算法引入遮挡多边形的概念,利用遮挡多边形判断曲面上离散点的隐藏性,同时将潜在隐藏线段与遮挡多边形求交,从而得到该线段的实际隐藏部分。该绘制算法对以网格模型显示三维物体具有通用性。  相似文献   

6.
多裁剪自由曲面生成有限元网格的实现   总被引:1,自引:0,他引:1  
张苏  施法中 《软件学报》2005,16(11):2008-2013
论述了多裁剪自由曲面生成有限元曲面网格的几个关键技术.采用了推进波前法生成曲面网格,给出了核心算法;在曲面算法中运用了介于参数法与直接法之间的新方法.针对求解曲面上最优点的参数域反算问题,引入了切矢逆求方法,可使迭代次数大为降低.测试表明,该算法快速、稳定.对大型的多裁剪自由曲面生成的曲面有限元网格,可直接用于有限元计算.  相似文献   

7.
为处理地质界面之间的空间相交关系,提出一种新的针对三角地质曲面的快速求交方法。该方法融合优化八叉树法和OBB搜索树方法,可以更快速准确地剔除远离交线的其他三角形。求交剩余的三角形得到交线,应用三角网局部重构和网格优化算法修正交线附近的三角网,最终分割交线两侧的地质曲面,完成2个地质曲面的离散化求交过程。与AABB、OBB和空间分解法相比,该方法在大数据量三角曲面求交中效率优势明显,可以快速准确处理地质模型构建和分析中的曲面求交问题,为三维地质模型自动化构建的实现提供有效支撑。  相似文献   

8.
海量散乱点的曲面重建算法研究   总被引:86,自引:0,他引:86  
基于海量散乱点的曲面重建在机械产品测量造型、计算机视觉、根据切片数据的医学图像重建等领域中有重要应用.给出了一种以物体表面上不附加任何几何和拓扑信息(包括测点法矢、曲面边界信息)的散乱点集为处理对象,自动生成物体表面的三角网格模型的算法.该算法首先根据测点的邻近测点估算曲面在该测点处的法矢,并采用优化的顺序对法矢方向进行调整以使各测点处的法矢都指向曲面外侧,最后用步进立方体算法输出三角网格模型.采用新的方法计算切平面,不但进一步提高了效率,而且改善了曲面边界及尖锐棱边区域的重建效果.还提出并解决了法矢方向传播中可能出现的局部“孤岛”问题.同时,提出了一种对海量数据进行空间划分的算法,从而大大提高了海量数据的处理效率.应用实例表明,算法效果良好  相似文献   

9.
本文应用B网分裂加密的思想,讨论在计算机上快速实现二元三方向网格上三角域样条曲面的显示。该算法具有快速、稳定和高效率等优点,可用于相应的曲面设计与曲面求交。  相似文献   

10.
有理三角曲面的分片线性逼近在参数曲面的求交、绘制等方面有着重要应用.已有研究主要采用曲面的二阶导矢界来估计逼近误差,而有理曲面的导矢界估计是一项困难的工作.为解决上述问题,利用齐次坐标,给出了一种定义域为任意三角形的有理三角曲面的分片线性逼近算法.该算法有效地避免了有理三角曲面的导矢界估计,并且离散段数可先验地给出.此外,通过重新参数化技术来缩小有理三角Bézier曲面的权因子之间的比值,进一步提高了算法的效率.  相似文献   

11.
A new algorithm based on the sweep plane approach to determine the machined part geometry in 5-axis machining with general APT tools is presented. Undercut and overcut can be determined. Collision detection between the toolholder, workpiece and workpiece fixture can also be detected. The subtraction of the removed material is obtained for each sweep plane by using a stencil buffer. A flat plane is swept through the blank part, fixture and tool swept volume geometry. The intersections of sweep planes and the swept tool volume are computed based on the canonical representation of a cone, torus and sphere. The necessary data to compute all the intersections is stored in a text file, here called the M-Plane file (Memory Plane). The equations of the intersections are approximated by a polygon with variable accuracy. The resulting APT tool intersection in each sweep plane is then clipped against the blank workpiece intersection with the current sweep plane. The stencil buffer provides automatically the union of all tool intersections and the subtraction from the blank workpiece. This algorithm provides a 3D geometric model of the tool swept volume. The display algorithm is based on the Painter's algorithm, but there is no time consuming sorting from back to front required, as the sweep proceeds from back to front. The accuracy of the algorithm can be varied as a function of the requirements by changing the polygon approximation and the distance between the sweep planes.  相似文献   

12.
直线与刀具扫描体求交算法及其应用研究   总被引:15,自引:2,他引:13  
直线与刀具扫描体的交点问题是数控图形验证,加工过程仿真技术中的核心问题,本文根据五坐标联动机床的运动特点,把刀具扫描体表达成几组简单曲面的组合,利用直线与这几类曲交点来求解直线与刀具扫描体的交点。利用该算法,我们开发了一个用于检验五坐标铣削加工精度的计算机领导具软件。加工与仿真的实践证明,该算法计算正确正确,对进一步研制开发加工过程仿真系统有重要意义。  相似文献   

13.
5-Axis sculptured surface machining is simulated using discrete geometric models of the tool and workpiece to determine the tool contact area, and a discrete mechanistic model to estimate the cutting forces. An extended Z-buffer model represents the workpiece, while a discrete axial slice model represents the cutting tool. Determination of the contact area for a given tool move requires a swept envelope (SWE) of the tool path. The SWE is used to find the intersections of the tool envelope with Z-buffer elements (ZDVs) representing the workpiece. A 3-axis approximation of the 5-axis tool movement is used to simplify the calculations while maintaining a desired level of accuracy. The intersection of the SWE with each ZDV yields segments which are used to find the contact area between the cutter and the workpiece for a given tool path. The contact area is subsequently used with the discrete force model to calculate the vector cutting force acting on the tool.  相似文献   

14.
数控加工过程的计算机仿真技术研究*   总被引:2,自引:0,他引:2  
基于计算机图形学技术,提出了一种数控加工过程的仿真算法。该算法将刀具扫描体和被加工零件表示成同一方向上的长方体单元,以简化布尔运算和提高仿真速度,并在微机上实现了数控加工图形仿真的全过程。  相似文献   

15.
In this paper, we present a methodology to generate swept volume of prevailing cutting tools undergoing multi-axis motion and it is proved to be robust and amenable for practical purposes with the help of a series of tests. The exact and complete SV, which is closed from the tool bottom to the top of the shaft, is generated by stitching up envelope profiles calculated by Gauss map.The novel approach finds the swept volume boundary for five-axis milling by extending the basic idea behind Gauss map. It takes piecewise C1-continuous tool shape into account. At first, the tool shape is transformed from Euclidean space into Tool map (T-Map) on the unit sphere and the velocity vector of a cutter is transformed into Contact map (C-Map) using Gauss map. Then, closed intersection curve is found between T-Map and C-Map on the Gaussian sphere. At last, the inverse Gauss map is exploited to get envelope profile in Euclidean space from the closed curve in the range. To demonstrate its validity, a cutting simulation kernel for five-axis machining has been implemented and applied to mold and die machining.  相似文献   

16.
In numerically controlled (NC) machining simulation, a Z-map has been frequently used for representing the workpiece. Since the Z-map is usually represented by a set of z-axis aligned vectors, the machining process can be simulated through calculating the intersection points between the vectors and the surface swept by a machining tool. In this paper, we present an efficient method to calculate those intersection points when automatically programmed tool-type tools move along a linear tool path. Each of the intersection points can be expressed as the solution of a system of non-linear equations. We transform this system of equations into a single-variable equation, and calculate the candidate interval in which the unique solution exists. We prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the non-linear equations within a given precision. The whole process of NC simulation is achieved by updating the Z-map properly. Our method can improve accuracy greatly while increasing processing time negligibly in comparison with previous Z-map update methods, making it possible to verify the tool path more accurately and reliably.  相似文献   

17.
A mechanistic model for 5-axis surface machining with a toroidal-end mill is presented in this work. A graphical representation of the tool movements is used to determine the in-process chip geometry and tool edge contact length using an adaptive and local depth buffer. The graphical representation of the tool movements is generated using either tooth swept sectors that model the tool’s cutting teeth as they rotate or the swept surface of the tool as it moves along the tool path. The mechanistic model was verified with two cutting experiments: The first cutting test showed that the data agrees with the simulation results within 7% of the peak-to-peak forces. The second cutting test modelled a more complex stock surface and tool path. The simulation results were within 10% of the measured peak-to-peak cutting torque.  相似文献   

18.
This paper presents a swept envelope approach to determining tool position for five-axis ruled surface machining. The initial tool position is traditionally located to contact with two directrices of a ruled surface. The swept profile of the tool is then determined based on the tool motion. By comparing the swept profile with the ruled surface, the tool position is corrected to avoid machining errors. The cutter's swept envelope is further constructed by integrating the intermediate swept profiles, and applied to NC simulation and verification. This paper presents the explicit solution for the swept profile of a taper-end cutter in five-axis ruled surface machining. The relation of the ruled surface geometry, the tool motion and the machining errors is developed. Therefore, the error sources can be detected early and prevented during tool path planning. The explicit swept envelope indicates that the machined surface is not a ruled surface in five-axis ruled surface machining. Manufacturing industries should take extra care in high precision ruled surface machining. Computer illustrations and example demonstrations are shown in this paper. The results reveal that the developed method can accurately position tool location and reduce machining errors for five-axis ruled surface machining.  相似文献   

19.
SWEEP曲面中三种定位标架的分析比较   总被引:7,自引:2,他引:5  
在基于SWEEP的几何造型中,一个基本的问题是运动路径上活动标架的确定,尤其对于运动路径是空间曲线的情况情形,它直接影响到所生成 S WE EP曲面的形状控制,在其它应用中,也直接影响到运动物体的形状和姿态的调整,到目前为止,已经有几种活动标架的确定方法,但它们对路径曲线的要求和所生成的SWEEP曲面的形状效果是不同的,文中比较了三种不同的活动标架,用实例说明了这些标架之间的差别,并在实用系统中实现。  相似文献   

20.
Determining a tight bounding volume of all the surface normal vectors is of interest in surface modelling especially for intersection problems, in order to detect closed intersection curves. It is also important to determine quickly whether two such volumes intersect. This paper adresses both problems through the introduction of a pyramid with a convex planar base. For intersection problems, a different method has been proposed by M. Hohmeyer. The various solutions are discussed and compared.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号