Virtual reality prototyping of bio-molecules

Modelling, sharing and transmission of three-dimensional (3D) graphics data of biomolecules are essential in many bio visualization tasks from collaborative research and education to molecular simulation and drug discovery. In the current paper, modelling and representing of bio-molecular structure for virtual and physical rapid prototyping is presented. Our aim is to devise a uniform solution for visualizing, browsing, interacting and prototyping of bio-molecules in various environments including internet, immersive virtual reality (VR), and rapid manufacturing. To do so, we use non uniform rational B-spline surfaces (NURBS) to represent protein secondary structure and surface structure. NURBS protein structures are then tessellated to form bio-molecular graphics models. Their triangular mesh representation is next extracted from their scene graph. A geometric optimization process is followed to make data compatible for their formatting in compact and consistent VR standard to support protein internet browsing, protein VR visualization, protein 3D rapid prototyping and crystal sub-surface laser engraving.     

An Internet-enabled image- and model-based virtual machining system

Virtual reality (VR) can be described as a four-dimensional (4-D) simulation of the real world, including the 3-D geometry space, 1-D time and the immersive or semi-immersive interaction interface. VR applications in mechanical-related research areas are becoming popular, e.g. virtual layout design, virtual prototyping, Internet-based virtual manufacturing, etc. However, research in VR applications is facing conflicting requirements for high rendering quality and near real-time interactivity. This paper represents an Internet-based virtual machining system that builds an integrated VR scene, which combines images and models, to overcome the above conflicts. This research is divided into three parts: first, image mosaics techniques are used to implement an Internet-based virtual workshop, which is an image-based virtual scene. The method of obtaining original sequential images, the principle of image mosaics to realize automatic seamless stitching, and projection transformation matrices to reconstruct a closed inward-facing space are presented. Secondly, a model-based virtual milling machine has been constructed with three detailed approaches: a category-based dynamic graph structure to support collision detection, a relation-oriented collision detection method to improve the efficiency of collision detection, and a dynamic modelling method to model a dynamic workpiece object. Finally, an Internet-based virtual milling system, which is the integration of the image-based virtual workshop and the model-based virtual CNC machine, is constructed using the reposition method to achieve visual consistency of the virtual objects and images. This system, which includes an integrated scene, combines the advantages of image-based VR and model-based VR. Consequently, this system has both high rendering quality and good real-time interactivity.     

贵州少数民族文化遗产的逆向工程应用研究

以少数民族文化遗产的保护和开发方法研究为目的,从实物测量、三维CAD模型、曲面模型评价体系、CAD模型重建等方面详细阐述了逆向工程技术在文化遗产保护方面的应用.选用有代表性的贵州少数民族文物--布依族酒壶、水壶以及木制傩戏面具作为研究对象,采用Hiscanner 激光扫描测头对其进行数据采集,扫描得到的点云数据可刻录到光盘上作为文物数据永久保存;更进一步地,采用目前流行的逆向工程软件Geomagic studio对点云数据进行数据精简、数据滤波、数据修补、提取特征线等处理后得到NURBS曲面;为保证曲面模型重建的精度,在曲面重建模型后对其误差评价,通过控制误差的方式指导曲面模型重建,使重建的文物曲面模型能真实完整地反映原状;最后,在功能强大的三维造型软件Solidworks中导入重构的NURBS曲面进行曲面缝合、放样等,将其生成实体CAD模型,并对模型的局部特征进行适当的再设计以实现文物实体模型的优化.对该模型进行快速成型制造可得到文物复制品或成品模具,即实现逆向工程技术在文化遗产保护中的应用研究.逆向工程技术应用于少数民族文化遗产文物保护是一个全新的课题,该项技术的应用能进一步推动文化遗产保护措施的发展,也能为类似课题的研究提供借鉴.     

Voxelization and fabrication of freeform models

We present a volume graphics system for the generation of freeform models and synthesis of complex objects. A unique non-uniform rational B-spline (NURBS) volume representation and its voxelization algorithm are proposed. The forward difference technique is employed to speed up the voxelization process while the desired topological connectivity is preserved. For synthesis of our models and other three-dimensional objects, such as computed tomography images, voxel-based cutting tools are developed for the AutoCAD user interface. Volume rendering is applied to visualize the intermediate and final models. An isosurface is then extracted over the synthesized model and exported to a rapid prototyping machine as an STL file for fabrication. The approach taken in this system has been proven robust and efficient in modelling and fabrication of complex freeform models.     

Virtual Reality Environments for Integrated Systems Health Management of Rocket Engine Tests

Integrated Systems Health Management (ISHM) consists of processes managing erroneous conditions that systems may encounter during their operational life by either designing out failures early on or defending and mitigating any possible failures. A successful implementation of ISHM consists of the following four components: data sensors, computations, data sinks, and visualization modules. In this paper, we explore the use of virtual reality (VR) platforms as a candidate for developing ISHM visualization modules. VR allows for a complete and spatially accurate 3-D model of a system to be displayed in real time. It provides a medium for improved data assimilation and analysis through its core tenants of immersion, interaction, and navigation. Furthermore, VR allows for integrating graphical, functional, and measurement data in the same platform—providing for the development of subsequent risk-analysis modules. The research objectives of this paper are focused on creating a detailed visual model of a multisensor rocket engine test facility inside a VR platform and demonstrating the capability of the VR platform in integrating graphical, measurement, and health data in an immersive, navigable, and interactive manner. A human-based performance evaluation of the VR platform is also presented. These research objectives are addressed using an example of a multisensor rocket-engine portable test stand at the National Aeronautics and Space Administration (NASA) Stennis Space Center's E-3 test facility.      

复杂地质曲面三维插值—逼近拟合构造方法

针对水利水电工程多源地质数据的特点,充分考虑了地质精度要求、曲面连续性和数据存储量等多方面的均衡,提出并实现了基于NURBS(non-uniform rational B-splines,非均匀有理样条曲线)技术的复杂地质曲面插值—逼近拟合构造方法。该方法对于工程关键区域集中且均匀分布的原始数据,采用NURBS蒙皮插值方法,使曲面严格通过这些数据点;对于周边区域分布离散的数据,采用NURBS逼近拟合方法,使曲面在给定精度下充分逼近原始数据;最后对整体曲面的地质结构合理性、几何性和精度进行检查分析和调整。实例表明,该方法所构造的地质曲面能满足地质工程师的实际需要,并能为进一步的三维地质建模提供基础。     

3D Flash Display for STL Model in Rapid Prototyping System

A kind of 3D color graphics display system for the STL model is developed by calling the functions from Open GL graphic library through VC 6. 0 under the Windows environment in this paper. The STL model is a high quality one that can be quiescent or animated. This system is conducive to find out the disfigurement of the STL model in a rapid prototyping process and to repair it, Therefore, the component quality can be enhanced.     

水利水电工程三维数字地形建模与分析

以锦屏一级水电工程为例，分别利用Delaunay算法和多细节层次技术实现了坝区地形TIN模型和施工总布置区域巡航所需的多分辨率地形模型。并根据三维地质建模的特殊需要，引入了NURBS技术对TIN地形模型进行了简化，所获得的NURBS地形模型不仅存储量小，精度损失低，而且易于图形操作运算，便于可视化分析，满足多方面的要求。该模型的实现与成功应用，在很大程度上推动了水利水电工程向着数字化、可视化和智能化的方向发展。     

Measuring in Virtual Reality: A Case Study in Dentistry

For application specialists to accept virtual reality (VR) as a valid new measuring environment, we conducted several case studies. This paper describes a case study in dentistry in which VR is used to measure the length of the root canal of a tooth from processed tomography data. This paper shows the advantages of measuring in visualization space rather than in reality. We present a software framework aimed at the application specialist rather than the VR expert. Furthermore, the VR measuring technique is analyzed and compared to traditional measuring techniques for this particular application. We show that VR allows for intuitive measuring paradigms that are accurate and versatile alternatives to situations where traditional techniques are deficient.     

应用Java3D技术构造网络虚拟现实环境的方法

Java3D是Java语言在三维领域扩展的一组API,可用于快速构建虚拟现实环境.通过比较两种创建虚拟现实环境的方法,提出一种利用Java3D技术创建虚拟现实环境的方法.着重介绍了利用Java3D构建虚拟现实环境的几个关键技术和具体实现方法,并实现了一个原型系统,同时给出了系统结构和功能.用户可以利用该系统非编程快速搭建所需的三维场景,并且能实现人与场景的交互.     

Optimized stereo reconstruction of free-form space curves based on a nonuniform rational B-spline model

Analytical reconstruction of 3D curves from their stereo images is an important issue in computer vision. We present an optimization framework for such a problem based on a nonuniform rational B-spline (NURBS) curve model that converts reconstruction of a 3D curve into reconstruction of control points and weights of a NURBS representation of the curve, accordingly bypassing the error-prone point-to-point correspondence matching. Perspective invariance of NURBS curves and constraints deduced on stereo NURBS curves are employed to formulate the 3D curve reconstruction problem into a constrained nonlinear optimization. A parallel rectification technique is then adopted to simplify the constraints, and the Levenberg-Marquardt algorithm is applied to search for the optimal solution of the simplified problem. The results from our experiments show that the proposed framework works stably in the presence of different data samplings, randomly posed noise, and partial loss of data and is potentially suitable for real scenes.     

基于VTK的激光跟踪测量可视化软件设计

测量数据的三维可视化是激光跟踪测量数据处理的关键步骤之一。结合大型激光跟踪测量软件系统的开发实践,对VTK技术特点和体系结构进行深入研究,设计实现了对测量数据进行处理和显示的类和接口。在此基础上,基于Microsoft Visual Studio 2010平台,利用C++和VTK技术开发了一款三维测量数据处理及可视化软件,实现了测量点云拟合、三维图形显示以及交互功能,并通过实例验证了软件的有效性和可用性,证明了VTK在工业测量可视化领域具有很大的应用价值。     

基于虚拟样机和粒子系统仿真技术的虚拟布线方法

将虚拟样机技术应用于机电产品电缆布线问题,提出了虚拟布线方法。该方法首先根据设计方案建立产品虚拟样机、电缆连接列表、电缆接口、电缆材料、截面参数等信息,基于上述信息以及电缆布线规范,利用虚拟样机技术对可视化和人机交互能力的支持规划出卡箍位置和电缆路径,进而计算电缆长度,在此基础上利用粒子系统仿真技术计算电缆形状,据此生成相应的电缆模型。在探讨了机电产品电缆布线问题及其求解思路的基础上,着重研究了机电产品的信息模型及虚拟布线的关键技术。通过一个实例证明了该方法的可行性。     

Hand-held 3D scanner for surface-shape measurement without sensor pose tracking or surface markers

Current hand-held three-dimensional (3D) scanners for surface-shape measurement require sensor-tracking devices or surface markers to determine the position and orientation (pose) of the sensor at different viewpoints, thus limiting their functionality. This paper presents a hand-held 3D scanner without sensor tracking or surface markers. Multiple planes of light are simultaneously projected onto an object surface to provide sufficient surface information to enable surface fitting and fine interpolation between acquired data points. In surface scanning, the hand-held scanner acquires a sequence of dense overlapping range-images from different viewpoints with enough overlap between range views and abundant information within each range view to permit registration of all acquired data into a single 3D model. Calibration is performed by closed-form surface-fitting to map 2D image coordinates to 3D calibration-object coordinates. Conical diffraction adjustment corrects for projected-line curvature. The measurement accuracy was suitable for applications such as reverse engineering, and virtual and physical prototyping.     

3D NURBS‐enhanced finite element method (NEFEM)

This paper presents the extension of the recently proposed NURBS‐enhanced finite element method (NEFEM) to 3D domains. NEFEM is able to exactly represent the geometry of the computational domain by means of its CAD boundary representation with non‐uniform rational B‐splines (NURBS) surfaces. Specific strategies for interpolation and numerical integration are presented for those elements affected by the NURBS boundary representation. For elements not intersecting the boundary, a standard finite element rationale is used, preserving the efficiency of the classical FEM. In 3D NEFEM special attention must be paid to geometric issues that are easily treated in the 2D implementation. Several numerical examples show the performance and benefits of NEFEM compared with standard isoparametric or cartesian finite elements. NEFEM is a powerful strategy to efficiently treat curved boundaries and it avoids excessive mesh refinement to capture small geometric features. Copyright © 2011 John Wiley & Sons, Ltd.     

基于虚拟样机技术月球机器人运动仿真

采用“虚拟样机”技术,建立一个集三维实体设计,动力学建模,控制,可视化仿真于一体的虚拟月面计算机仿真环境,对月球机器人的静力学,运动学以及动力学进行仿真研究,为月球机器人结构参数,动力学参数及控制算法的优化提供了设计参数和验证场所。     

小型回旋加速器虚拟样机技术

小型回旋加速器虚拟样机技术是把小型回旋加速器的理论计算、分析、信息技术与机械设计、加工、装配、调试、运行、维修等专家知识进行有机结合，在系统仿真和虚拟现实基础上发展起来的一种新概念技术。基于虚拟样机，可以实现创新设计，有效降低探索风险。文章探讨了回旋加速器虚拟样机系统框架，讨论了虚拟样机系统的体系结构和回旋加速器产品的全生命周期仿真，提出了基于全生命周期集成和多学科协同设计的回旋加速器虚拟样机的开发思路。     

Design of high performance badminton shuttlecocks: virtual and rapid prototyping approach

In this paper, a framework utilising virtual and rapid prototyping to aid design of a shuttlecock skirt was proposed and implemented. A standard template for flow simulation on ANSYS® CFX was developed to predict the aerodynamic performance of the virtual prototypes, with focus on reduced simulation time and complexity. This forms the basis of the computer aided design model – computational fluid dynamics – performance evaluation loop in the proposed framework. Steady state flow simulation was conducted for three simple computer aided design models of shuttlecocks, with different gap dimensions on the skirt. Wind tunnel drag study of the models reproduced through rapid prototyping validated the simulation result. The proposed methodology can also be applied to the existing design process for integration of virtual and rapid prototyping to reduce the burden of design iteration.     

快速成型技术在家具设计中的应用研究

目的探索快速成型技术与传统木工工艺的邂逅,在家具产品设计中的应用。方法运用分析、比较的研究方法,了解3D打印快速成型技术的优势,探讨传统工艺与3D打印技术相结合的表现效果。结论通过不断探索快速成型技术与传统工艺的结合,在3D打印这一现代技术的影响下,"新"、"旧"技术的结合将成为家具设计创新的突破口,并基于模块化的设计理念,推导出家具产品创新设计的思路与方法。