基于连接点的二维多角弧匹配

多角弧匹配问题的关键是，其既能反映多角弧的几何性质，又能反映多角弧拓扑结构的特征选取．在分析了多角弧几何形状的基础上，引入了连接点的概念，并用连接点集表示多角弧，这一表示在旋转和平移变换下是不变的。进一步取该连接点集作为匹配的特征集，给出了特征集之间匹配的算法．该算法是将连接点间的距离积分作为测量函数，使二维多角弧的匹配由连接点的匹配来决定．给出的模拟试验结果表明，该算法效果良好，并且对于数值污染具有健壮性。     

Online Personalised Non‐photorealistic Rendering Technique for 3D Geometry from Incremental Sketching

This paper presents an online personalised non‐photorealistic rendering (NPR) technique for 3D models generated from interactively sketched input. This technique has been integrated into a sketch‐based modelling system. It lets users interact with computers by drawing naturally, without specifying the number, order, or direction of strokes. After sketches are interpreted as 3D objects, they can be rendered with personalised drawing styles so that the reconstructed 3D model can be presented in a sketchy style similar in appearance to what have been drawn for the 3D model. This technique captures the user's drawing style without using template or prior knowledge of the sketching style. The personalised rendering style can be applied to both visible and initially invisible geometry. The rendering strokes are intelligently selected from the input sketches and mapped to edges of the 3D object. In addition, non‐geometric information such as surface textures can be added to the recognised object in different sketching modes. This will integrate sketch‐based incremental 3D modelling and NPR into conceptual design.     

Development of a semantic product modeling system for initial hull structure in shipbuilding

In the initial stage of ship design, designers represent geometry, arrangement, and dimension of hull structures, which correspond to product model information, with 2D geometric primitives such as points, lines, arcs, and drawing symbols on 2D drawings. However, designers must translate the product model information defined on the 2D drawings more intelligently in the following design stages. Thus, design semantics could be lost and design processes that follow could be delayed because of errors by mistranslating the information. Here, design semantics mean design intents of the designer, that is, functions and structures which the product must have.In this study, a semantic product model data structure of an initial ship hull structure was proposed, and a semantic product modeling system was developed based on the proposed data structure. The proposed data structure can store semantic product model information such as product design results with the use of 2D wire frame geometrical data, part attributes, and design knowledge. Hence, this information can be used to generate a 3D solid model and production material information for CAPP as needed.The applicability of the proposed data structure and the developed system was verified by applying them to the deadweight 300,000 ton of Very Large Crude oil Carrier’s product modeling procedure. The application results showed that the proposed data structure and the developed system can be efficiently used for overall initial ship design environment.     

基于参数化设计的三维桥梁模型构建

参数化设计是几何体建模的重要手段,而桥梁的三维可视化是当今桥梁信 息化的发展趋势。论文针对桥梁外观参数化模型可视化的需要,对几何体参数化建模的原理 和方法进行了深入探讨。结合桥梁结构特点,分析了主要桥梁组件结构（如T 梁、盖梁柱 式墩、轻型桥台等）构件图的几何和拓扑关系,对组件进行了参数化设计,实现组件的三维 建模;并对组件中特殊图元（如圆弧倒角形墩柱、桥台近似锥面护坡）的绘制算法进行详细 研究;根据各组件间空间位置的拓扑关系,利用参数化变量驱动计算各组件空间位置坐标, 进行桥梁的快速拼接。完成的桥梁三维参数化建模以参数为驱动,用户可以对设计结果进行 可视化修改。所实现的三维参数桥梁可视化系统具有模型构建精致,参数化建模彻底、建模 速度快,参数分类清晰,可视化效果好的特点。     

Using geometric constraints through parallelepipeds for calibration and 3D modeling

This paper concerns the incorporation of geometric information in camera calibration and 3D modeling. Using geometric constraints enables more stable results and allows us to perform tasks with fewer images. Our approach is motivated and developed within a framework of semi-automatic 3D modeling, where the user defines geometric primitives and constraints between them. In this paper, first a duality that exists between the shape parameters of a parallelepiped and the intrinsic parameters of a camera is described. Then, a factorization-based algorithm exploiting this relation is developed. Using images of parallelepipeds, it allows us to simultaneously calibrate cameras, recover shapes of parallelepipeds, and estimate the relative pose of all entities. Besides geometric constraints expressed via parallelepipeds, our approach simultaneously takes into account the usual self-calibration constraints on cameras. The proposed algorithm is completed by a study of the singular cases of the calibration method. A complete method for the reconstruction of scene primitives that are not modeled by parallelepipeds is also briefly described. The proposed methods are validated by various experiments with real and simulated data, for single-view as well as multiview cases.     

基于草图交互的个性化服装生成方法

以建立和交互修改三维服装草图为设计手段，提出在三维人体模型上生成三维个性化服装的参数化造型方法．服装草图由2种基本几何元素组成：体现人体围度信息的封闭样条曲线和体现人体在高度方向上曲面形状过渡的不封闭样条曲线．将服装草图约束分为2类4种：一类是体现服装宽松程度的人体与服装曲面之间的间隙约束；另一类是服装几何元素本身之间的共点、共面与对称约束．从人体的特征点出发，通过间隙约束生成服装草图的几何元素；在共点、对称和共面约束下，由服装草图几何元素建立拓扑结构为四边网格的服装草图．服装草图的交互修改是草图约束维护的过程，构建侧视图、正视图、断面图3个视图组成草图修改平台，在平台上交互编辑特征曲线．服装曲面则以三维草图为框架，通过对四边网格双线性Coons曲面插值生成．提供的设计方法使服装的造型变得简洁、灵活．     

基于连接点的3D多角弧匹配

为了满足实际应用的要求，快速地进行多角弧匹配是必要的，因此，提出了一种快速的3D多角弧表示和匹配的方法。该方法是在分析多角弧几何形状基础上，引入连接点的概念，同时，通过在连接点处建立局部直角坐标系来得到每一连接点处的球面坐标。并用连接点的球面坐标集表示多角弧，因这一表示在旋转和平移变换下是不变的，所以可取该球面坐标集作为多角弧匹配的特征集，用该特征集可保持多角弧的几何属性和拓扑结构。这样3D多角弧匹配就降为1D数值串匹配，从而使使匹配变得简单快速。其测量函数为对应连接点间的均方差。实验结果表明，该匹配算法效果良好，并且对于数值污染具有健壮性。     

一种含设计意图的3D模型数据实时交换格式

为了在不同商用3D CAD系统之间实现含设计意图的几何模型数据的网上实时交换,提出了一种基于XML描述的数据交换格式,可将参考面的定位数据与局部坐标、组成轮廓草图的图元数据与约束关系、特征的构建形式与构建过程以层次结构化的方式包含在交换数据中,满足了同构与异构CAD系统之间实时交换含设计意图的数据之需要.     

符号方案三维实体化的自动化方法研究

如何将创新设计过程中得到的符号方案生成直观的图形方案，是机械概念设计中的关键技术问题，通过对符号方案的邻接矩阵元素进行分析，得到机构的结构组成、构件连接关系等信息；运用符号方案的尺度矩阵确定各装配构件的二维几何尺度，在面向对象二次开发的环境下，基于三维参数化平台，实现构件的三维实体化；根据构件所处空间位置，按后台预置装配方法得到三维虚拟实体装配图。上述过程基于面向对象的环境，输入／读入概念设计得到符号方案后，系统自动地将符号方案生成三维虚拟实体方案。