Sketching 3D models with 2D interaction devices

The creation of a 3D shape using CAD tools, namely solid modelers, is difficult and time-consuming. Therefore, these systems are kept away from the conceptual phases of design, perhaps the most important in any product life cycle. The sketch is considered by many people as one of the fundamental techniques during a design's conceptual stages, as it enables high level design options to be explored at low cost. In general, this technique IS under-appreciated in the computer graphics world. In this paper, we present a system called IDeS that tries to combine simplicity and intuition while drawing, with the useful features of the solid modelers, for example, CSG operators.     

三维几何造型系统工程图模块的设计

二维CAD支撑软件系统模型巳经处于成熟的阶段，作为集标准化、智能化为一体的面向图形设计与绘图的集成系统，巳具有良好的互操作性和伸缩性，为了秉承扩张其优点，讨论分析了二维CAD支撑软件系统和三维几何造型系统体系结构和数据结构，并在二维CAD支撑软件系统模型和流程控制机制基础上设计了实现三维几何造型系统中的工程图模块。     

2D and 3D shape retrieval using skeleton filling rate

As an increasing number of digital images are generated, a demand for an efficient and effective image retrieval mechanisms grows. In this work, we present a new skeleton-based algorithm for 2D and 3D shape retrieval. The algorithm starts by drawing circles (spheres for 3D) of increasing radius around skeletons. Since each skeleton corresponds to the center of a maximally inscribed circle (sphere), this process results in circles (spheres) that are partially inside the shape. Computing the ratio between pixels that lie within the shape and the total number of pixels allows us to distinguish shapes with similar skeletons. Experimental evaluation of the proposed approach including a comprehensive comparison with the previous techniques demonstrates both effectiveness and robustness of our algorithm for shape retrieval using several 2D and 3D datasets.     

Computer aided clothing pattern design with 3D editing and pattern alteration

The traditional apparel product development process is a typical iterative ‘optimization’ process that involves trial-and-error. In order to confirm the design and achieve a satisfactory fit, a number of repeated cycles of sample preparation, trial fitting and pattern alteration must be conducted. The process itself is time-consuming, costly, and dependent on the designer’s skills and experience. In this paper, a novel computer aided design (CAD) solution for virtual try-on, fitting evaluation and style editing is proposed to speed up the clothing design process. A series of new techniques from cross parameterization, geometrical and physical integrated deformation, to novel editing methods are proposed. First, a cross parameterization technique is employed to map clothing pattern pieces on a model surface. The pattern can be precisely positioned to form the initial shape with low distortion. Next, a new deformation method called hybrid pop-up is proposed to approximate the virtual try-on shape. This method is an integration of geometrical reconstruction and physical based simulation. In addition, user interactive operations are introduced for style editing and pattern alteration in both 2D and 3D manners. The standard rules regulating pattern editing in the fashion industry can be incorporated in the system, so that the resulting clothing patterns are suitable for everyday production.     

基于形式语法的建筑设计细胞衍生法研究

目前可用的计算机辅助设计工具,为设计开发过程后期阶段提供了相当有效地支 持,但对于设计初始阶段,即设计思路成熟、但设计的结构和形状还未确定之时,需要一种新 的CAD 解决方案来支持设计者思维方式并激发创作灵感。因此,提出一种基于空间形式语法的 建筑设计生成方法,描述复杂空间形体如何自动派生--通过限定的规则产生初始体块,在规 则内生成与初始体块相似体块,再而改变局部可变规则生成多样复杂的系统,同时允许设计者 积极参与整个生成过程。以CFS 墙体原型建模为例,验证该参数化建模方法的有效性和可行性。     

一种二维工程图向三维模型的尺寸映射算法

针对当前制造型企业内部存在二维工程图和三维CAD模型之间的数据共享问题,提出一种基于图匹配的二维工程图向三维CAD模型的尺寸映射算法,将二维工程图中的尺寸信息直接映射到对应的三维CAD模型上。首先将三维模型进行投影得到投影视图,然后将投影视图和二维工程图转化为一种空间关系图,对两个空间关系图进行图匹配,找出图元间的映射关系,并且利用工程图中尺寸标注的特点对算法进行改进,提高算法效率和可靠性。实验结果表明,该算法可以很好的实现二维工程图向三维CAD模型的尺寸映射。     

CAD中三维交互技术的研究与实现

本文研究了ＶＲ技术在ＣＡＤ几何造型中作为交互手段的应用,特别研究了三维交互技术在ＣＡＤ中的实现。通过提出一种用于三维交互的精确视觉线索方法,实现了对三维空间中不同信实体相互位置关系的精确感知。探讨了ＣＡＤ中在三维交互技术支持下的新的几何造型技术。     

箱体类塑件注射模三维造型方法

基于ＡｕｔｏＣＡＤ Ｒ１２工作平台,以箱体类塑件为对象开发了一种注射模ＣＡＤ系统,该系统提出了一种新的高级体素单元－切片体素;提出了利用二维塑件图形来获得三维塑件几何造型的图形数据输入方法和能完成复杂成型零件的三维几何造型技术;设计了相关的系统数据库接口,实现了系统各模块内部数据的集成统一等关键技术;给出了模具三维装配造型和装配图纸生成实例。     

CAD for process plants: an update

We review the availability of CAD software for the process design activities of physical properties generation, unit operation design, flowsheeting and dynamic flowsheet simulation. Similarly we look at CAD software for materials control, piping documentation and pipe stressing. We report conclusions drawn from our research into the provision and use of CAD turnkey systems for producing schematics at the conceptual design phase, and for equipment specification, layout, piping design and 3D modelling at the engineering design phase.By reviewing the shortcomings of current CAD systems along with developing CAD technology, we were able to specify the requirements of the next generation of process plant CAD.     

Shape-It-Up: Hand gesture based creative expression of 3D shapes using intelligent generalized cylinders

We present a novel interaction system, “Shape-It-Up”, for creative expression of 3D shapes through the naturalistic integration of human hand gestures with a modeling scheme dubbed intelligent generalized cylinders (IGC). To achieve this naturalistic integration, we propose a novel paradigm of shape–gesture–context interplay (SGCI) wherein the interpretation of gestures in the spatial context of a 3D shape directly deduces the designer’s intent and the subsequent modeling operations. Our key contributions towards SGCI are threefold. Firstly, we introduce a novel representation (IGC) of generalized cylinders as a function of the spatial hand gestures (postures and motion) during the creation process. This representation allows for fast creation of shapes while retaining their aesthetic features like symmetry and smoothness. Secondly, we define the spatial contexts of IGCs as proximity functions of their representational components, namely cross-sections and the skeleton with respect to the hands. Finally, we define a natural association of modification and manipulation of the IGCs by combining the hand gestures with the spatial context. Using SGCI, we implement intuitive hand-driven shape modifications through skeletal bending, sectional deformation and sectional scaling schemes. The implemented prototype involves human skeletal tracking and hand posture classification using the depth data provided by a low-cost depth sensing camera (Kinect?). With Shape-It-Up, our goal is to make the designer an integral part of the shape modeling process during early design, in contrast to the case for current CAD tools which segregate 3D sweep geometries into procedural 2D inputs in a non-intuitive and onerous process requiring extensive training. We conclusively demonstrate the modeling of a wide variety of 3D shapes within a few seconds.     

基于手绘输入理解的智能3D几何建模系统

近年来,图形学领域已经开发了大量的3D建模和可视化工具,但是这些工具的界面往往过于复杂,制约了设计人员的创造性工作,也进一步限制了这些工具为普遍用户所使用。事实上,理想的3D建模工具应该提供给用户以尽可能自然、简单的操作,例如基于电子笔的草图输入,而且随着移动设备的发展,也使之成为图形学中更有前景的研究方向。文章论述了当前支持手绘的建模技术的研究现状,并提出了一个更加智能化的多模块建模体系,突出了交互技术、智能理解和高质量的可视化输出技术的结合;而且针对手绘输入的不明确性,着重分析了图形数据的基于特性的语义描述,提出了智能的逻辑推理模型,并进一步描述了下一代融合自然输入、逻辑推理与虚拟显示于一体的智能图形建模系统的实现。预测了人工智能技术与CA D技术的结合将是未来图形学领域发展的主要方向之一。     

TeCo3D—Sharing Interactive and Dynamic 3D Models

In this paper we present a method for sharing interactive and dynamic 3D models that are collaboration-unaware, i.e., models that have not been designed to be used by multiple users at the same time. This functionality is an essential requirement for the inclusion of arbitrary 3D models, as generated by standard CAD or animation software, into teleconferencing sessions. A key aim of this work is to show that a large part of the required functionality can be developed in a way so that it is reusable for other applications such as shared whiteboards or networked computer games. Our method therefore consists of both an application dependent part that handles the specific tasks required for sharing 3D models, and of a number of generic services such as synchronization, scalable support for latecomers, and the ability to record and replay sessions. The generic services are based on an abstract media model and the RTP/I application level protocol for distributed interactive media. Any other application for a medium that shares this model and that uses RTP/I may reuse these generic services. We have implemented a prototype called TeCo3D demonstrating the feasibility of our approach.     

基于虚拟现实的三维园林景观设计仿真系统

现有的园林景观专业CAD软件对三维模型及虚拟仿真效果表达有限,只能进行二维施工图绘制.为解决动态景观特性,研发了虚拟现实技术的三维园林景观设计仿真系统,采用面向对象的参数化三维实体建模手段,实现了三维实体建模、设计场景的三维实时虚拟呈现、渲染图及动画制作、施工图绘制等功能,并探索了系统计算原理、实现方法及OpenGL扩展功能等相关技术.然后简要介绍了系统整体功能,详细论述了专业模块中的仿真过程.最后以工程实例验证了系统的有效性.     

Partial 3D Shape Retrieval by Reeb Pattern Unfolding

This paper presents a novel approach for fast and efficient partial shape retrieval on a collection of 3D shapes. Each shape is represented by a Reeb graph associated with geometrical signatures. Partial similarity between two shapes is evaluated by computing a variant of their maximum common sub-graph.
By investigating Reeb graph theory, we take advantage of its intrinsic properties at two levels. First, we show that the segmentation of a shape by a Reeb graph provides charts with disk or annulus topology only. This topology control enables the computation of concise and efficient sub-part geometrical signatures based on parameterisation techniques. Secondly, we introduce the notion of Reeb pattern on a Reeb graph along with its structural signature. We show this information discards Reeb graph structural distortion and still depicts the topology of the related sub-parts. The number of combinations to evaluate in the matching process is then dramatically reduced by only considering the combinations of topology equivalent Reeb patterns.
The proposed framework is invariant against rigid transformations and robust against non-rigid transformations and surface noise. It queries the collection in interactive time (from 4 to 30 seconds for the largest queries). It outperforms the competing methods of the SHREC 2007 contest in term of NDCG vector and provides, respectively, a gain of 14.1% and 40.9% on the approaches by Biasotti et al. [ BMSF06 ] and Cornea et al. [ CDS*05 ].
As an application, we present an intelligent modelling-by-example system which enables a novice user to rapidly create new 3D shapes by composing shapes of a collection having similar sub-parts.     

三维CAD环境下的产品数据管理方法

分析三维CAD中基本数据类型,并抽取面向管理的结构化信息;定义了数据问的关系类型及数据生命周期状态;给出数据约束和关联定义．结合CAD数据的生命周期管理,提出关联数据在进行出库、入库、发布等方面的操作时,相关数据进行自动更新的规则．针对CAXA实体设计系统给出管理数据模型,并在SMARTEAM平台上实现．     

钢结构节点三维实体技术

针对钢结构节点设计和施工图绘制需要大量构造细节的问题,应用钢结构节点的三维实体技术,研发相应的钢结构后处理系统.采用模板的概念与方法表达各种形式的钢结构节点,用三维实体技术构造钢结构节点及构件的三维计算机模型.该系统作为钢结构专业CAD软件3D3S的核心技术已经成功应用于数千项实际工程的施工详图设计中,实用性很强.     

超二维环境下尺寸驱动和参数设计的研究

超二维环境的最大特点在于使用了二维数据表示三维模型，实现了不建立三维模型直接对三维模型的各向投影进行参数设计，直接修改复杂工程图，由于相对三维工程实体，纯二维数据信息量不足，而按以往方法用多视图来弥补，又因视图间缺乏必要联系，无法建立和描述三维信息，因而，超二维模型引入视图投影信息，使之具有一定的三维信息。通过结合当前尺寸驱动和参数设计的现状，在超二维环境下，引和高等画法几何学多视图间的投影原理，     

以用户为中心的三维桌面导航系统设计

提出一种基于模拟真实工作环境创建下一代图形用户界面的方法,建立了可扩展的三维交互空间,通过引入具有质量、体积、颜色和摩擦系数等物理属性的三维物件,采用碰撞检测和刚体动力学技术,开发了一套以用户为中心的三维桌面导航系统--UCDN.用户评估表明,该方法可用性高、趣味性强,为新一代图形用户界面提供了积极的探索.     

Random Exploration of the Procedural Space for Single-View 3D Modeling of Buildings

In this paper we tackle the problem of 3D modeling for urban environment using a modular, flexible and powerful approach driven from procedural generation. To this end, typologies of architectures are modeled through shape grammars that consist of a set of derivation rules and a set of shape/dictionary elements. Appearance (from statistical point of view with respect to the individual pixel’s properties) of the dictionary elements is then learned using a set of training images. Image classifiers are trained towards recovering image support with respect to the semantics. Then, given a new image and the corresponding footprint, the modeling problem is formulated as a search of the space of shapes, that can be generated on-the-fly by deriving the grammar on the input axiom. Defining an image-based score function for the produced instances using the trained classifiers, the best rules are selected, making sure that we keep exploring the space by allowing some rules to be randomly selected. New rules are then generated by resampling around the selected rules. At the finest level, these rules define the 3D model of the building. Promising results on complex and varying architectural styles demonstrate the potential of the presented method.