复杂雕刻型面特征建模

通过对复杂雕刻型面的分析，提出了三种特征定义方法：类别定义法、功能定义法与形状定义法。探讨了雕刻实体特征描述方法，并提出用“轨迹包络法”来描述雕刻实体特征几何信息，建立了雕刻型体特征的“双链四表”数据结构及其拼合、贴合、嵌套、扭变等四种拓扑关系，并建立了相应的特征模型。     

平面闭合图形的光滑雕刻型面建模

雕刻型面建模是数字化艺术雕刻工艺中重要且复杂的环节.为快速、高质量地建立适应于数字化雕刻的光滑曲面模型,提出一种基于平面闭合图形,采用二次Bézier曲线与细分网格的建模方法.首先分5种情况对约束Delaunay三角化后的闭合图形进行处理,然后在相应的区域上建立二次Bézier曲线族,用直线在另一方向连接所有Bézier曲线上的细分点,以形成覆盖相应区域的细分网格曲面.实验结果表明,该方法能够快速地建立光滑的雕刻型面,满足数字化雕刻的实际需求.     

一种高度真实感型体的建模方法

型体对虚拟场景的表现起着很重要的作用 ,目前对型体的建模一般采用直接将型进行拉伸的办法 ,这种处理方法存在真实感不高的缺点 .本文对高度真实感型体建模流程进行分析 ,提出了如何构造与获取型体截面的方法 ,对型体截面采用曲线插值的方法获取型体截面多边形 ;基于截面多边形与多边形相邻边构成三角形的方向 ,特别提出勾边算法对型体的截面多边形进行勾边处理 ,以消除由于前后表面与拉伸面直接过渡所造成的边缘陡变 ,利用原始截面多边形与勾边处理过的截面多边形构造真实感型体 .并最终给出一些实例来说明方法的有效性     

泰森多边形及其在等深面生物量计算中的应用

介绍了泰森多边形的原理和算法实现，并举例说明了它在计算洪湖任一等深面平均生物量中的应用。实践证明，泰森多边形是一种有效的由点到面的内插方法，在基于抽样观测的资源与环境研究中有其独特的作用     

非规则数据场体绘制光线投射求交的加速新方法

光线投射是非规则数据场体绘制的一种常用方法。它能生成高质量的图形，但开销很大。其原因在于光线与面的求交，特别是与外部面的求交，需要非常大的工作量。本文利用平面多边形扫描算法求取光线与外部面的交点，井利用内部体元和面的相关性，改进了光线与内部面的求交计算，从而减少了运算量，提高了绘制速度。     

基于二次Bezier曲面的图像雕刻型面建模

针对纹理清晰且结构较简单的图像,依据其灰色或彩色像素信息,利用二次Bezier曲面直接构建雕刻型面模型。该方法通过对图像进行分割,分析和计算图像子块的像素值及位置参数,作为构建模型曲面片的特征参数,并对曲面片采用一种有限光滑拼接方法实现建模。构建的雕刻型面模型能够表述图像中原物体的基本结构特征,并能满足数字化雕刻加工的需要。算法复杂度较低,实用性强是该建模方法的特点。     

木工数字化智能雕刻系统关键技术的研究

现有雕刻机系统在复杂3D雕刻花纹的建模、二维图象或图形到3D模型的自动转换及3D实物的仿制等方面的功能大大受到限制,使得数字化雕刻在古典家具、石才、木材、建筑装饰材料等需求艺术雕刻的的行业难以得到推广应用.本文针对木工数字化艺术雕刻的特点,就复杂雕刻型面一体化智能建模、建立以中国传统雕刻花纹为主的雕刻图形数据库等关键技术提出了解决方案和实现途径,构建的系统更具智能化、敏捷化和实用性,能满足高品质、大批量雕刻艺术产品的需要.     

CNC电脑雕刻机及其与数控铣床和加工中心的联合应用策略

雕刻加工是饱含着人类高智能和高技能的工匠型劳动，当代雕刻制造技术正经历着从手工雕刻BCNC雕刻的变革。本文较为详尽地讲述了CNC电脑雕刻机与数控铣床、加工中心在机器结构、控制系统、应用软件等方面的区别，并介绍了它们在模具型芯加工中的联合运用策略。[编者按]     

木工数字化智能雕刻系统关键技术的研究

一、引言 数控雕刻机系统在机加工和模具等行业已得到广泛应用,并产生显著效益,但现有系统对复杂3D(三维)型面花纹的建模设计与雕刻加工、3D雕刻实物的仿制和图形图象的智能化处理、产品动态仿真和虚拟制造等能力的缺乏,使得现有雕刻机在需求艺术雕刻的众多领域的推广应用举步蹒跚.     

用于二维不规则排样的离散临界多边形模型

提出了一个用于求解二维不规则排样问题的离散临界多边形模型.Burke等人的BLF算法是求解排样问题的一种有效算法,但其算法对一些特殊实例会产生非法的解.为了解决这个问题,提出了一种基于离散临界多边形模型,并对其正确性作了严格证明.新模型是只含有点和区间的简单模型,在大大降低原问题几何复杂性的同时,也使许多启发式策略可以更容易地求解该问题.计算结果表明,基于离散临界多边型模型的排样算法是很有效的.     

Computing non-self-intersecting offsets of NURBS surfaces

A new approach for the computation of non-self-intersecting offset surface of a single G₁ continuous NURBS surface has been presented. The approach recognizes special surfaces, i.e. planes, spheres, cones and cylinders, and offsets them precisely. An approximate offset surface within the specified tolerance is computed for a general free form surface. The method for a general free form surface consists of (1) sample offset surface based on second derivatives; (2) eliminate sample points which can give self-intersections; (3) surface fitting through the remaining sample points; and (4) removal of all the removable knots of the surface. The approach checks for self-intersections in the offset surface and removes the same automatically, if any. The non-self-intersecting offsets for surface of extrusion and surface of revolution are obtained by removing the self-intersections in the offset generator and profile curves respectively using point sampling, cleaning of sampled points, curve fitting and knot removal. The approach has better control on error. It generates offset surface with less number of control points and degree. The methodology works only for a class of problems where in the offset of a single G₁ surface is still a single connected surface without having any holes. The offset methodology has been demonstrated through three types of surfaces namely surface of revolution, surface of extrusion and a general free form surface. This approach has been extensively used in creation of offset surfaces of composite laminate components. The presented approach can also be used to check for self-intersections in any general surface and to remove the same, if any, with little modifications, as long as the cleaned surface is a single connected surface.     

应用高斯曲率积分的曲面可展化分片方法研究

对空间曲面的分片算法进行了研究,以高斯曲率的绝对值对面积的积分与曲面面积的比值作为曲面分片系数,并以各曲面单元分片系数的和作为曲面分片的控制值。在给定分片控制值的约束条件下,通过对任意空间曲面进行离散化、反算拟合及曲面单元累加实现曲面分片。控制各曲面片分片系数累加值使之小于一定的控制值以使各分片近似可展。以空间双曲曲面为算例对分片算法的有效性进行了验证。     

Ricci flow-based spherical parameterization and surface registration

This paper presents an improved Euclidean Ricci flow method for spherical parameterization. We subsequently invent a scale space processing built upon Ricci energy to extract robust surface features for accurate surface registration. Since our method is based on the proposed Euclidean Ricci flow, it inherits the properties of Ricci flow such as conformality, robustness and intrinsicalness, facilitating efficient and effective surface mapping. Compared with other surface registration methods using curvature or sulci pattern, our method demonstrates a significant improvement for surface registration. In addition, Ricci energy can capture local differences for surface analysis as shown in the experiments and applications.     

复杂曲面笔式加工的直接插补算法

复杂曲面笔式加工时的工具轨迹是位于曲面上的自由曲线轨迹．针对此类形式的轨迹，给出一种复杂曲面笔式加工时的自由曲线型刀轨的直接插补算法，即对位于曲面上以投影方式形成的任意自由曲线形式的刀轨进行插补计算，生成控制机床运动的指令．该方法的实现扩充了CNC系统的轨迹控制功能，提高了复杂曲面的加工效率．仿真和试切的结果证明算法可行而且有效．该算法也可以应用到整体曲面加工中．     

NURBS surface deformation design for complex products by transplanting the surface feature

This article addresses the problem of NURBS surface deformation design using surface feature transplantation. To represent the semantic surface feature, a new surface feature representation called normal feature membrane is proposed. In the proposed method, the base surfaces of the source surface with the feature that the designer is highly interested in and the target surface to be deformed are first constructed. This is followed by extracting the normal feature membrane of the source surface. The deformation design is then realized by transplanting the extracted normal feature membrane of the source surface to the base surface of the target surface through four main operations, which are normal feature membrane preprocessing, normal feature membrane transplanting, surface fairing, and boundary feature decaying, respectively. The proposed method provides an easy copy–paste operation of the semantic surface feature for surface deformation of complex product. The examples of the surface feature transplantation for the surface design of automobile bodies are given to verify the validity and feasibility of the proposed method.     

类螺旋特征测点数据的闭曲面建模方法研究

复杂曲面及海量点云测量数据的曲面建模已成为通用CAD/CAM软件的重要功能;然而,对于复杂的闭曲面建模方法,仍然存在许多技术上的难题,至今尚未能很好的解决,比如,基于海量的测量数据,如何进行闭曲面特征点识别,如何进行区域分割与处理,这一切都使得闭曲面建模过程中很难采用已经成熟的自由曲面建模技术和方法.通过研究异步仿形测量原理以及测量数据类型,针对鞋楦测量形成的空间螺旋线数据特征,提出一种闭曲面建模方法.该方法包括如下步骤:首先对测量点数据处理;并以特征螺旋线数据为基础对曲面进行三角分割;最后,以三角Bezier曲面为基础进行曲面构造,并将各曲面进行拼接、裁剪,形成完整的曲面.采用该方法对鞋楦测量数据的建模实例说明,能够有效地对具有空间螺旋线数据特征的闭曲面进行数据处理、曲面重构,提高了产品建模效率.     

Novel method for measuring surface tension

It is shown that the observed geometry of an electrostatic deformation of a liquid surface can be used for the measurement of surface tension. Based on simulations and measurements, an empirical formula for the relation between the shape of the deformation and the surface tension is derived and discussed. A novel method for high resolution measurements of the surface tension using interferometry of an electrostatically deformed liquid surface is presented and investigated.     

基于轮廓数据的B样条曲面重建

针对B样条曲面拟合中出现的问题和困难,提出了一种基于行组织的轮廓数据（截面数据）的曲面重建方法。该方法避免了数据点的参数化问题,使得逼近曲面拥有较好的形状和合理的控制顶点数量。该方法的基本思想是：首先构造易于控制的低阶曲面拟合数据点,此曲面称控制曲面,然后利用高次曲面逼近该曲面,此高次曲面称为逼近曲面,为所需要的重建曲面。在曲面重建中利用最佳平方逼近和光顺函数,减少了逼近曲面的控制顶点冗余,较有效地防止了逼近曲面的形状突变和曲面的扭曲,很大程度地提高了曲面的质量。     

A surface based approach to recognition of geometric features for quality freeform surface machining

The paper presents a surface-based approach for geometric feature recognition for the purpose of automating the process planning of freeform surface machining. The proposed approach consists of the following four steps for recognition of the geometric features: conversion and preprocessing of the surface geometry data, subdivision of NURBS surface, reconstruction of surface orientation areas, and recognition of geometric features. The proposed scheme assumes that the input geometry data form is based on an IGES CAD model and the surface model can be represented in the form of trimmed NURBS surfaces. The connectivity relations of the product surfaces are analyzed and each surface is subdivided into orientation regions based on the surface normal vector over a certain point density grid, and then all the connected regions with the same orientation type are grouped into surface orientation areas. After that, the geometric feature will be recognized through the analysis of area connectivity and relationship. The paper describes the developed algorithms on surface orientation region subdivision, surface orientation area reconstruction, and geometric feature recognition. The verified feasibility study of the developed method is also presented.     

具有规整曲率线网的光滑曲面设计

为了设计具有规整曲率线网且无脐点的光滑曲面,提出一种曲面交互设计算法。 采用 Bézier 曲面片光滑拼接构成的复合曲面作为表达形式,通过交替曲率线网的优化和曲面细 分得到自由形状的设计曲面,所得曲面具有规整曲率线网而且没有脐点。以此复合 Bézier 曲面 为基础,通过圆纹样条曲面优化算法得到结构规整的圆纹样条曲面,同时也能得到圆锥曲面条 模型以及曲面多层支撑结构等自由建筑曲面设计中有重要应用的几何结构。