平面复杂花纹图案的3D建模算法研究

通过对平面复杂花纹图像或图形的矢量化处理或数据转换,得到平面复杂花纹图案清晰轮廓的数据矩阵,然后采用扫描分析法求出扫描线与轮廓线的交点,并进行配对和中点计算;运用二次Bezier曲线构建其3D模型数据矩阵,再对模型数据进行后期优化处理,最终生成平面复杂花纹图案的3D模型.该建模方法能够构想和创建平面花纹图案的虚拟模型,生成光滑细腻的模型曲面和具有图案基本结构特征的逼真模型,并能灵活控制模型生成的形态.建模算法具有复杂度低、建模速度快、实用性强等特点.     

基于聚类的三维模型检索算法

将聚类算法应用于三雏模型对称特性的提取上,实现三维模型的检索.对三维模型表面进行采样,根据采样点计算三维模型的对称平面,通过聚类算法得出三维模型实际的对称平面,以此对称特性作为三维模型的特征信息,进行三维模型的检索.     

基于力反馈技术的三维模型表面绘制技术研究

本文将力反馈技术引入虚拟绘制过程中,提出一种基于力反馈技术的三维模型表面绘制方法。首先分析毛笔在三维绘制过程中的受力和变形,采用弹簧-振子模型建立三维毛笔模型;然后由毛笔碰撞变形后的最小包围球找出碰撞相关点,计算碰撞相关点的平均法矢确定投影平面,通过计算毛笔的变形得出在投影平面上的笔触,将该笔触投影到三维模型表面,同时控制毛笔的受力和运笔路径叠加笔触获得具有特定书法效果的三维笔道;最后介绍了仿真系统,使用Phantom Desktop力反馈设备在该系统中实现了三维模型表面的绘制。仿真结果表明,该方法再现了三维模型表面绘制的力觉控制过程,增强了绘制过程中的真实感。     

基于表面提取的三维重建方法

本文提出了一种人机交互重建平面立体的新方法。该方法通过从视图上直接提取三维面,并由三维面导出三维点和三维边的方法建立平面立体的边界表示模型。这种方法具有重建速度快,为三维造型提供了一个便捷的手段。     

基于侧影轮廓的三维模型快速重建

提出一种基于侧影轮廓进行三维模型重建的新方法,将传统的三维锥形交叉问题转换成二维轮廓交叉问题。首先,将不同视角下的二维侧影轮廓反投影到若干个平行的三维平面上,然后在三维平面上计算所有反投影轮廓的交叉轮廓,最后对相邻三维平面上的交叉轮廓进行匹配并重建物体的表面。理论分析和实验结果表明该算法的时间复杂度和视角数目呈线性关系。由于该方法主要以增加视角数目来提高模型的精确度,所以比三维锥形交叉的方法能更快速地重建物体精确的三维模型。     

基于三角网格模型的纹理映射研究

纹理映射可以在不增加三维模型复杂度的前提下很好地表现三维模型表面的纹理细节,提高三维模型的视觉效果。针对三维网格模型,提出一种用基于纹理图册的方法将模型进行分片,并利用最小二乘保形映射对分割得到的每一片进行平面参数化,控制了形变。再通过建立二维坐标系与纹理坐标系的关系,确定三维模型各个顶点的纹理坐标,从而对三维模型进行纹理映射。实验证明,该方法能得到较好的纹理映射效果,增强了三维模型的真实感。     

基于点线关系从透视画隐线图重构三维平面立体

提出了一种基于点与直线关系从透视投影画隐线图建立平面立体线框模型的新方法。给出了基于点线关系的基本约束,根据透视投影画隐线图中隐含的点与直线位置关系建立约束方程,建立一个线性系统,通过求解该线性系统得到平面立体的三维信息。用算例进行验证,得到了平面立体的三维信息。     

基于三角网格模型的局部纹理映射

局部纹理映射可以增添三维模型的局部细节,加强模型的真实感。为了实现对三维模型的局部特征描写,增强局部纹理映射的用户可交互性,提出一种基于区域增长和平面投影的方法来实现三角网格模型的局部纹理映射。区域增长是以指定的三角面片为初始种子面片,搜索与种子面片共顶点的增长规则扩散出待映射区域。算法不仅保证了选取区域的完整性,不会出现缺角的情况;同时用户可以改变待映射区域的位置和大小。采用平面投影法对待映射区域进行纹理映射,将三维顶点投影到基准平面上,建立二维坐标系与纹理坐标系的关系,从而确定三维顶点和纹理坐标的对应关系。算法成功应用于实验,表明该方法的可行性。     

城镇无人机高分辨率三维网格图形建模仿真

针对利用Auto、Constructor和Max Surf软件建立的城镇高分辨率三维网格图形模型,普遍存在建立时间长,建模成本高的问题,为此提出无人机高分辨率三维网格图形建模.通过无人机采集城镇平面图像,在UG环境下完成城镇平面图像的三维建模.建模过程中,通过对城镇原始图像的提取及处理,得到三维实体模型,利用透射反射网格图像线条,将远场域网格和旋转域网格转换成过度网格截面,以适用于不同复杂度的城镇网格图形,实现城镇无人机高分辨率三维网格图形建模.仿真结果表明,城镇无人机高分辨率三维网格图形建立模型所用时间短,成本低,分辨率高,适用能力强,对于无人机采集城镇图像具有重要意义.     

飞机拦阻过程的三维动画模拟

提出了一种可行的建立飞机拦阻装置三维视景动画的方法。首先,通过Creator建立三维模型,然后,利用Vega将各个模型统一于同一场景下,再利用Lynx设置飞机降落轨迹,其中拦阻网部分通过Opengl产生拦阻网和飞机一起运动的效果。最后,整体构架通过它们之间的接口统一于VC,建立起逼真的飞机拦阻三维视景动画模拟系统,该系统较好地展现了飞机拦阻过程。通过实际对比分析,较之平面仿真具有更好的直观性和实用性。     

Simulating Wood Using a Voxel Approach

In this paper we present a technique for generating three-dimensional wood textures using a regular texture array. Currently three-dimensional wood textures are generated using procedural textures. Procedural textures are flexible and require little memory, however the modeling of local artifacts such as knots is difficult using the procedural approach. By representing the wood as a texture array and growing the wood in this array we can easily simulate local phenomena such as knots. Our growth model is an approximation to the biological model and assumes that there are several similar wood cells per array element. This means that we can model artifacts that are defined by groups of similar cells. In particular our model is well suited for the modeling of soft-woods.     

矿井通风系统三维模型的构建与应用

现有的巷道三维模型建模算法复杂,且以巷道两端端点坐标直接确定巷道的走势,不能较好地体现巷道的起伏。针对上述问题,以煤矿工程平面图为基础数据,利用巷道间的拓扑关系进行定位点采集,采用中心线加载断面的算法构建了矿井三维巷道模型。基于矿井三维巷道模型,将通风设施模型同步到三维系统中,生成了矿井通风系统三维模型及相应数据库,生成的立体图能清晰地展示矿井巷道的整体走势,结合数据库信息管理可对矿井模型进行添加、修改等智能操作。实际应用结果表明:该模型实现了矿井通风系统二维图到三维图的快速转换,可真实地展示煤矿巷道信息及工作面状况,生成的矿图数据库可实时更新,为研究矿井通风网络解算和灾变模拟提供了优良平台。     

基于网络图的地基激光雷达复杂树木点云枝叶分离方法

地基激光雷达树木点云数据的枝叶分离是精确计算地上生物量和叶面积指数的重要前提,也是树木三维建模的重要步骤.然而,山地复杂树木冠幅大且结构复杂,从而造成树叶与枝干之间的相互遮挡,因此很难获取高质量的点云数据,目前对其实现枝叶分离依然存在较大的困难.利用地基激光雷达FARO Focus3D X330获取三维激光点云数据,提...     

考虑参数优化的BTT导弹三维非线性制导律

针对BTT（bank-to-turn）导弹制导过程中的通道耦合问题,设计了一种考虑制导参数优化的新型的三维非线性制导律.首先,采用旋量描述方法构建弹目视线方位模型,采用矢量描述方法构建弹目视线角速度模型,从而得到了导弹制导的三维非线性模型;然后,将制导律分为制导控制项和耦合补偿项.基于制导控制项最优设计相应的目标函数.同时,在不损失制导信息的情况下,将制导模型转化为线性形式;最后,分别针对无终端约束和有终端约束情况,基于二次型最优方法得到了三维制导律.该制导律既解决了通道解耦,其制导参数又满足一定物理意义下的最优性.仿真结果验证了本文所设计制导律的有效性.     

过程纹理造型技术在自然物体仿真中的应用

通过对过程纹理造型技术的应用以木材为例成功地对其纹理作了仿真模拟。并给出了由所提炼出的相关数学模型得出的仿真算法。现在比较常用的构造三维纹理的基本方法有两种：基于高频采样的数字化纹理和采用数学模型动态计算生成纹理。基于高频采样的数字化纹理由于需要有三维数组的支持,在处理高分辨率的纹理时占用空间将急剧增大,多数场合对此是无法忍受的。在真实感较好的一些图形合成系统中多采用数学模型动态计算生成纹理的纹理定叉方法。经过多年的研究实践已经开发积累了许多过程迭代函数以产生各种复杂的纹理,这些过程纹理（Procedural Texture）函数被证明是非常有效的,成功模拟了木材、大理石．云彩、火焰和石板等许多自然物体的纹理。     

基于OpengL的面向对象的巷道三维可视化

介绍了巷道三维模型建立的过程,即巷道数据处理、巷道三维实体模型、模型OpengL映射、三维场景设置、坐标投影变换、巷道三维显示。采用面向对象的VC++的结构体数据类型和类建立描述组成巷道中心线的不同基本元素空间信息的数据结构。利用OpenGL原语进行描述,对巷道实体三维数学建模。通过三维场景设置,控制三维巷道的生成效果,运用OpenGL的Z缓存自动消隐功能构建和生成具有真实感的三维巷道模型,并实现交互式查询。以此解决方案对地下巷道的实际情况进行直观和形象的模拟,对煤矿的信息化管理能力有一定的提高,利于指导煤矿的实际生产。     

Hierarchies based on the number of cooperating systems of three-dimensional finite automata

The question of whether processing three-dimensional digital patterns is much more difficult than two-dimensional ones is of great interest from both theoretical and practical standpoints. Recently, owing to advances in many application areas, such as computer vision, robotics, and so forth, it has become increasingly apparent that the study of three-dimensional pattern processing is of crucial importance. Thus, the study of three-dimensional automata as a computational model of three-dimensional pattern processing has become meaningful. This article introduces a cooperating system of three-dimensional finite automata as one model of three-dimensional automata. A cooperating system of three-dimensional finite automata consists of a finite number of three-dimensional finite automata and a three-dimensional input tape where these finite automata work independently (in parallel). Those finite automata whose input heads scan the same cell of the input tape can communicate with each other, i.e., every finite automaton is allowed to know the internal states of other finite automata on the cell it is scanning at the moment. In this article, we continue the study of cooperating systems of three-dimensional finite automata, and mainly investigate hierarchies based on the number of their cooperating systems.     

Surface flattening based on energy model

This paper presents a method for three-dimensional surface flattening, which can be efficiently used in three-dimensional computer aided garment design. First, a facet model is used to present a complex surface. Then, a spring-mass model based on energy function is used to flatten the 3D mesh surfaces into 2D patterns. The surface elastic deformation energy distribution is depicted by a color graph, which determines a surface cutting line. The method presented here can efficiently solve flattening problems for complex surfaces. The accuracy of a developed surface can easily be controlled locally. Thus, compared to earlier methods, this method provides more flexibility for solving CAD and CAM problems.     

Garment pattern generation from body scan data

An automatic garment pattern design system using three-dimensional body scan data has been developed. A body model has been generated from massive body scan data using segmentation and the Fourier series expansion method. The surface geometry of a standard garment model used in the apparel industry was reconstructed by stereovision technique and converted into a mesh structure. Surface warping algorithm was used to make an equalized geometry of two models, and multi-resolution mesh generation along with optimum planar pattern mapping algorithm were used to generate the optimum two-dimensional patterns of the garment.     

Integration of multiresolution image segmentation and neural networks for object depth recovery

A novel technique for three-dimensional depth recovery based on two coaxial defocused images of an object with added pattern illumination is presented. The approach integrates object segmentation with depth estimation. Firstly segmentation is performed by a multiresolution based approach to isolate object regions from the background given the presence of blur and pattern illumination. The segmentation has three sub-procedures: image pyramid formation; linkage adaptation; and unsupervised clustering. These maximise the object recognition capability while ensuring accurate position information. For depth estimation, lower resolution information with a strong correlation to depth is fed into a three-layered neural network as input feature vectors and processed using a Back-Propagation algorithm. The resulting depth model of object recovery is then used with higher resolution data to obtain high accuracy depth measurements. Experimental results are presented that show low error rates and the robustness of the model with respect to pattern variation and inaccuracy in optical settings.