基于笔交互的几何教学系统

随着电算化教学在广大中小学校中的推广,教师的板书教学同电算化教学之间的矛盾日益突出。针对这个问题该文基于人机交互中的笔交互技术,设计并实现了一套几何教学系统,并将双向几何约束的相关技术应用于该系统中。该系统有效地结合了当前教师丰富的板书教学经验和计算机对信息强大的处理能力,具有广阔的应用前景。     

三维交互任务的描述和结构设计

主要讨论了三维交互中交互任务的归纳描述和结构设计问题.首先归纳出三维交互中的基本交互任务和普遍交互任务,对二者之间的联系进行了描述,提出了一个三维交互任务的产生框架,最终建立起三维交互中通用的核心模块.三维交互核心模块描述了三维交互中通用的底层结构,模块中定义了三维交互中通用的一系列交互原语和交互任务,实现了原语的产生和任务的整合工作.在开发三维用户界面构造系统(3D UI toolkit或3D UIMS)或具体的三维/虚拟现实应用时,可以直接用它来建立系统的底层交互结构,而程序员将只关注于交互风格的建立等高层工作.     

面向虚拟装配的三维交互平台

针对当前装配领域的特点，提出一个面向虚拟装配的三维交互平台（Virtual Assembly Toolkit,VAT），VAT中包含了新的三维交互思想，定义了装配领域中常有的三维交互原语，设计和实现了交互原语的捕获，解释和处理框架，同时，VAT封装了三维图形构造，零件间的约束和碰撞检测等功能，VAT可以大大简化虚拟装配应用的构造，便于应用的快速生成。     

三维交互体系结构的研究与实现

针对当前人机交互特别是三维交互的现状基于分布式环境提出了一个分层的模型结构,分析了一般交互在各层中的基本行为,建立了与具体硬件设备无关的面向任务的事件模型,着重讨论了原始结构形成基本事件的方法,复合事件对基本事件的时间关系的整合以表达复杂的语义,在一般交互模型的基础上描述了三我互的8种基本任务,一切复杂的交互任务都是这8种基本任务在时间或空间上的语义整合,最后实现了分布环境下三维交互的一个原型系统Easy3D。     

桌面环境下的笔式三维交互框架

笔输入和三维交互结合是研究三维交互范型的一种新方法。提出一个桌面虚拟环境下的笔式三维交互框架,包含交互原语和交互任务构造两个核心组件。首先采用词法到语法的二级封装机制来生成高级事件和交互原语,然后综合交互上下文、用户修正和手势识别实现基本交互任务到复杂交互任务的整合机制。框架中内嵌的手势交互、约束感知和混合交互技术能有效降低任务分解和模式切换带来的认知负担,提高交互自然性。     

三维几何造型系统

1.系统结构及特点 我们研制了一种适用于微机的新颖的产品设计造型系统(PLAGE),该系统的三维部分结构见图1.由图可见,它能生成单个物体、相交曲面,也能生成装配体,经过消隐生     

分布式认知系统中的协同感知交互设计

本文提出的“分布式认知系统中的协同感知交互”以系统作为分析单元,考虑人与媒介、媒介与媒介之间的交互,强调系统中的各个构成要素的相互作用在交互过程中的重要地位,这对于减少人在交互过程中的认知负担、创造自然高效的交互环境具有一定的指导作用。     

三维几何模型数字水印综述

主要对近些年来在三维几何模型数字水印研究方面的算法进行了总结.首先给出了三维几何模型数字水印的一些基本概念,进而对三维水印在空域和变换域的典型算法进行了介绍,最后对三维几何模型的难点和发展前景进行了总结和展望.     

一种基于位置关系判定的GPU 三维几何图元拾取方法

针对交互式图形应用对拾取在效率、适用范围和拾取信息方面的需求,提出一种 新的基于GPU 的三维几何图元拾取方法。在进行拾取绘制时关闭光栅化,将鼠标位置信息和图 元顶点坐标变换到规范化设备坐标系,通过在几何处理器中判断投影后的二维图元与鼠标或选 择框的位置关系进行命中判定,并利用变换反馈将拾取信息返回应用程序。在提出方法的基础 上,介绍了单体拾取和块拾取的OpenGL 实现。实验表明,该方法的单体拾取效率较基于GPU 的射线相交法有约10%的提升,同时能支持高效块拾取。     

三维几何测量的自适应坐标系

分析了三维几何量测量中坐标系的建立方法，提出了刚性坐标系和柔性坐标系的概念，发展了三维几何量测量的一个新概念、新方法－自适应坐标系。仿真装配过程，坐标系具有自适应性，可使虚检率降低，提高经济效益。     

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.     

3D object perception using gradient descent

A new algorithm is presented for interpreting two-dimensional (2D) line drawings as three-dimensional (3D) objects without models. Even though no explicit models or additional heuristics are included, the algorithm tends to reach the same 3D interpretations of 2D line drawings that humans do. The algorithm explicitly calculates the partial derivatives of Marill's Minimum Standard Deviation of Angles (MSDA) with respect to all adjustable parameters, and follows this gradient to minimize SDA. For an image with lines meeting atm points formingn angles, the gradient descent algorithm requiresO(n) time to adjust all the points, while Marill's method requiredO(mn) time to do so. Experimental results on various line drawing objects show that this gradient descent algorithm running on a Macintosh II is one to two orders of magnitude faster than the MSDA algorithm running on a Symbolics, while still giving comparable results.     

A multimodal virtual reality interface for 3D interaction with VTK

The object-oriented visualization Toolkit (VTK) is widely used for scientific visualization. VTK is a visualization library that provides a large number of functions for presenting three-dimensional data. Interaction with the visualized data is controlled with two-dimensional input devices, such as mouse and keyboard. Support for real three-dimensional and multimodal input is non-existent. This paper describes VR-VTK: a multimodal interface to VTK on a virtual environment. Six degree of freedom input devices are used for spatial 3D interaction. They control the 3D widgets that are used to interact with the visualized data. Head tracking is used for camera control. Pedals are used for clutching. Speech input is used for application commands and system control. To address several problems specific for spatial 3D interaction, a number of additional features, such as more complex interaction methods and enhanced depth perception, are discussed. Furthermore, the need for multimodal input to support interaction with the visualization is shown. Two existing VTK applications are ported using VR-VTK to run in a desktop virtual reality system. Informal user experiences are presented. Arjan J. F. Kok is an assistant professor at the Department of Computer Science at the Open University of the Netherlands. He studied Computer Science at the Delft University of Technology, The Netherlands. He received his Ph.D. from the same university. He worked as a Scientist for TNO (Netherlands Organization for Applied Scientific Research) and as assistant professor at the Eindhoven University of Technology before he joined the Open University. His research interests are visualization, virtual reality, and computer graphics. Robert van Liere studied Computer Science at the Delft University of Technology, the Netherlands. He received his Ph.D. with the thesis “Studies in Interactive Scientific Visualization” at the University of Amsterdam. Since 1985, he has worked at CWI, the Center for Mathematics and Computer Science in Amsterdam in which he is the head of CWI’s visualization research group. Since 2004, he holds a part-time position as full professor at the Eindhoven University of Technology. His research interests are in interactive data visualization and virtual reality. He is a member of IEEE.     

Generating 3D interaction techniques by identifying and breaking assumptions

Researchers have created 3D interaction techniques for immersive virtual worlds, but existing techniques represent just part of the design space. While exploring other parts of the design space might yield more effective techniques, conducting that exploration is difficult and time-consuming. Analyzing the particular task, user, and hardware characteristics for any given problem is straightforward, but only suggests the shape of a potential technique; generating the technique itself still requires a creative breakthrough. We propose extending existing approaches to generating 3D interaction techniques by focusing more explicitly on identifying and breaking assumptions about the real world to inspire potential technique ideas. We describe our approach, suggest an initial list of assumptions to consider, and present a case study of applying the process to create a technique for navigation with visible landmarks and place representations.     

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。     

多用户VRML技术在构造3D人—人交互界面中的应用

提出了利用多用户ＶＲＭＬ技术构造ＣＳＣＷ系统中３Ｄ人－人交互界面,它能使用户间进行交互时获得虚拟现实的视听感觉,还提出了一个基于ＶＲＭＬ的３Ｄ人－人交互界面的基本框架,它适用于大多数ＣＳＣＷ系统。     

场景语义约束的三维交互技术

针对复杂虚拟环境下的交互需求,从面向高层应用的角度对交互任务进行分析,提出三维交互任务的层次模型。结合应用特点,将虚拟场景中的语义约束引入到三维交互技术的设计中,实现了多种面向高层应用的导航技术和选择操作技术,并在不同交互技术和操作隐喻模式之间实现了自然的融合和平滑的转换。用户界面利用这些语义约束更好地感知和理解用户的交互意图,实现更为直观、高效的三维交互过程。     

Construction of feature-matching perception in virtual assembly

An important characteristic of virtual assembly is interaction.Traditional direct manipulation in virtual assembly relies on dynamic collision detection,which is very time-consuming and even impossible in desktop virtual assembly environment.Feature-matching is a critical process in harmonious virtual assembly,and is the premise of assembly constraint sensing.This paper puts forward an active object-based feature-matching perception mechanism and a feature-matching interactive computing process,both of which make the direct manipulation in virtual assembly break away from collision detection.They also help to enhance virtual environment understandability of user intention and promote interaction performance.Experimentl results show that this perception mechanism can ensure that users achieve real-time direct manipulation in desktop virtual environment.     

利用辐射度模型实现冠层光合有效辐射分布

提出基于辐射度模型模拟单株虚拟植物冠层光合有效辐射分布的技术流程,采用半立方体算法计算辐射度模型的形状因子,逐步求精迭代法解辐射度线性方程组,计算虚拟植物模型任意空间位置的辐射度值和能量值。通过对比基于光线跟踪模型和辐射度模型模拟冠层太阳直射光合有效辐射,不仅发现基于两种模型的模拟结果具有较好的一致性,而且基于辐射度模型的模拟更具合理性。最后,分析冠层净光合速率进一步验证基于辐射度模型模拟冠层光合有效辐射的有效性。