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1.
针对机场净空管理中存在的可视化差、精细管理不足等问题,基于三维Cesium引擎研究机场净空保护区三维信息显示与管理等关键技术。首先,依据规范要求计算障碍物限制面的三维关键点,运用Cesium构建障碍物限制面及预警阈值面的三维模型;然后,通过分层分块组织、线性四叉树索引构建,基于优先等级的数据加载优化实现海量三维数据的调度;最后,以天津机场为例建立管理系统。运行效果表明:该系统可有效提升净空安全管理的数字化水平,为机场高效运行提供了有力保障。 相似文献
2.
针对整个模型统一尺度规划和曲面间的衔接处理困难问题,提出“曲面模型-三角网格模型-截面线-点集-测点集”的规划策略,实现基于曲率特性的自适应测点规划。通过将数字化设计模型转换成统一粒度的密集三角网格模型,实现复杂型面的一致性描述;进而利用三角网格的拓扑信息,提取截面线;在截面线曲率估算的基础上,通过均分曲线质量进行测量点的自适应规划。结果表明,该研究能以较少的测点反映加工误差。 相似文献
3.
A method for computing the visible regions of free-form surfaces is proposed in this paper. Our work is focused on accurately
calculating the visible regions of the sequenced rational Bézier surfaces forming a solid model and having coincident edges
but no inner-intersection among them. The proposed method calculates the silhouettes of the surfaces without tessellating
them into triangle meshes commonly used in previous methods so that arbitrary precision can be obtained. The computed silhouettes
of visible surfaces are projected onto a plane orthogonal to the parallel light. Then their spatial relationship is applied
to calculate the boundaries of mutual-occlusion regions. As the connectivity of the surfaces on the solid model is taken into
account, a surface clustering technique is also employed and the mutual-occlusion calculation is accelerated. Experimental
results showed that our method is efficient and robust, and can also handle complex shapes with arbitrary precision.
Project supported by the National Basic Research Program (973) of China (No. 2002CB312106) and the National Natural Science
Foundation of China (Nos. 60533070, and 60403047). The third author was supported by the project sponsored by a Foundation
for the Author of National Excellent Doctoral Dissertation of China (No. 200342) and a Program for New Century Excellent Talents
in University (No. NCET-04-0088), China 相似文献
4.
为了平滑曲面拼接中出现的奇点（或奇线），章提供一种割补法，即在奇线附近割去一小块曲面，同时补充一过渡曲面片，使曲面整体具有GC^1连续，并给出过渡曲面和原曲面接触程度和割补面积的计算方法。 相似文献
5.
溶洞旅游是旅游行业的一个重要组成部分,其具有稀缺性与不可复制性的特点。溶洞旅游开发过程中需要注意开发与保护的统一,传统测绘手段只能为设计单位提供2D数字绘图,不能详细反映溶洞内部细节情况,因此设计单位在设计时可能出现在某些空间上把握不准确,造成空间浪费甚至溶洞内部资源损坏的情况。借助地面三维激光扫描系统,通过前期控制测量,将扫描仪安置在控制点上对溶洞内部进行高精度扫描。以云南某溶洞旅游景区开发项目为例,阐述三维激光扫描技术在地下溶洞旅游开发中的具体应用,包括前期现场准备及作业方法、点云数据处理、复杂表面3D建模、精度评定、作业效率分析及经验总结等,以期为溶洞旅游开发提供一定参考。 相似文献
6.
地市级区域作为我国社区教育工作的落脚点,在推动社区教育工作中发挥着核心和关键作用,针对当前我国基层社区教育工作中存在的问题,设计构建地市级社区教育的组织架构体系、支持服务模式和数字化学习平台成为推动社区教育工作全面发展的重要策略和抓手,基于这种设计理念提出社区教育工作的运行保障机制也显得尤为重要。 相似文献
7.
为避免相邻图像非重叠区域特征点被检测和提取,加速图像配准,提出一种基于相位相关法与改进SURF算法的快速图像拼接方法。该方法采用相位相关算法确定待拼接图像的重叠区域,限定SURF特征点检测、提取范围,用改进的SURF算法进行特征点匹配|然后根据MSAC算法剔除误配后的特征点匹配对,求取单应性矩阵,实现图像之间的快速配准|最后采用多波段融合算法对配准后的图像进行处理以消除拼接缝。实验结果表明,与传统算法相比,该方法可提高特征点匹配正确率,加速图像配准过程,完成拼接图像间的平滑过渡。 相似文献
8.
INTRODUCTION Image fusion can be defined as the process by which several images, or some of their features, are combined together to form different modalities or instruments, and is of great importance in many ap- plications (Hall and Llinas, 1997; Zhou et al., 1998), such as object detection, ATR (Automatic Target Recognition), remote sensing, computer vision, and robotics. Recently some researchers recognized that it seems more meaningful to combine objects/regions rather than pixels… 相似文献
9.
In this study, a Surface Computer Supported Cooperative Work paradigm is proposed. Recently, multitouch technology has become widely available for human–computer interaction. We found it has great potential to facilitate more awareness of human-to-human interaction than personal computers (PCs) in colocated collaborative work. However, other studies and modern operating systems have rarely been concerned with colocated interactions in their user interface (UI) design. Therefore, one UI framework, which we have named Surface Application Framework (SAF), is proposed to support multitouch and multiuser applications on tabletop computers. To explore the effects of wide area SAFs on colocated collaboration, one application, capable of making English sentences, was developed based on an SAF. This application was used to conduct a user-centric study to investigate differences between surface computers and PCs. The results show that a surface computer performs better than a PC in creating awareness during collaborative work, but it requires more time due to its poor performance with drag-and-drop operations. Finally, this study summarizes a three-dimensional design approach to consider various trade-offs between awareness and manipulative performances. Additionally, some mechanisms are suggested to be employed to overcome the weakness of drag-and-drop operations with multitouch interfaces in a future study. 相似文献
10.
Burcu Arslan Yang Jiang Madeleine Keehner Tao Gong Irvin R. Katz Fred Yan 《Educational Measurement》2020,39(2):96-106
Computer-based educational assessments often include items that involve drag-and-drop responses. There are different ways that drag-and-drop items can be laid out and different choices that test developers can make when designing these items. Currently, these decisions are based on experts’ professional judgments and design constraints, rather than empirical research, which might threaten the validity of interpretations of test outcomes. To this end, we investigated the effect of drag-and-drop item features on test-taker performance and response strategies with a cognition-centered approach. Four hundred and seventy-six adult participants solved content-equivalent drag-and-drop mathematics items under five design variants. Results showed that: (a) test takers’ performance and response strategies were affected by the experimental manipulations, and (b) test takers mostly used cognitively efficient response strategies regardless of the manipulated item features. Implications of the findings are provided to support test developers’ design decisions. 相似文献
11.
For reconstructing a freeform feature from point cloud, a deformation-based method is proposed in this paper. The freeform feature consists of a secondary surface and a blending surface. The secondary surface plays a role in substituting a local region of a given primary surface. The blending surface acts as a bridge to smoothly connect the unchanged region of the primary surface with the secondary surface. The secondary surface is generated by surface deformation subjected to line constraints, i.e., character lines and limiting lines, not designed by conventional methods. The lines are used to represent the underlying information of the freeform feature in point cloud, where the character lines depict the feature＇s shape, and the limiting lines determine its location and orientation. The configuration of the character lines and the extraction of the limiting lines are discussed in detail. The blending surface is designed by the traditional modeling method, whose intrinsic parameters are recovered from point cloud through a series of steps, namely, point cloud slicing, circle fitting and regression analysis. The proposed method is used not only to effectively and efficiently reconstruct the freeform feature, but also to modify it by manipulating the line constraints. Typical examples are given to verify our method. 相似文献
12.
13.
吕淑婷 《渭南师范学院学报》2011,26(2):26-28
文章讨论了积分计算出现奇点时,通过巧妙的添加新的辅助线（面）,挖去奇点构造新的复连通区域的求积分方法,本质上是对相应的公式做了推广,从而使对各类积分公式的运用有更深层次的掌握,加强了对各类积分联系的理解． 相似文献
14.
CHEN Jun-hua WU Yi-jie 《浙江大学学报(A卷英文版)》2007,8(11):1789-1794
This paper focuses on the analysis of running conditions and machining processes of conical cam with oscillating follower. We point out the common errors existing in the design and machining of the widely used plane expansion method of conical cam trough-out line. We show that the motion can be divided into two parts, i.e. the oscillating motion of oscillating bar and the rotary motion of oscillating bar relative to the conical cam. By increasing the rotary motion of oscillating bar, the motion path of tapered roller on oscillating bar （i.e. contour surface of conical cam） can be expanded on the cylinder. Based on these analyses, we present a creative and effective designing and machining method for 3D curve expansion of conical cam with oscillating follower. 相似文献
15.
DAI Jun-fei KIM Junho ZENG Hua-yi GU Xian-feng YAU Shing-tung 《浙江大学学报(A卷英文版)》2007,8(10):1671-1680
We give the topology changing of the silhouette in 3D space while others study the projections in an image. Silhou- ettes play a crucial role in visualization, graphics and vision. This work focuses on the global behaviors of silhouettes, especially their topological evolutions, such as splitting, merging, appearing and disappearing. The dynamics of silhouettes are governed by the topology, the curvature of the surface, and the view point. In this paper, we work on a more theoretical level to give enu- merative properties of the silhouette including: the integration of signed geodesic curvature along a silhouette is equal to the view cone angle; in elliptic regions, no silhouette can be contained in another one; in hyperbolic regions, if a silhouette is homotopic to a point, then it has at least 4 cusps; finally, critical events can only happen when the view point is on the aspect surfaces (ruled surface of the asymptotic lines of parabolic points with surface itself). We also introduce a method to visualize the evolution of silhouettes, especially all the critical events where the topologies of the silhouettes change. The results have broad applications in computer vision for recognition, graphics for rendering and visualization. 相似文献
16.
Advances in computer and interface technologies have made it possible to create three‐dimensional (3D) computerized models of anatomical structures for visualization, manipulation, and interaction in a virtual 3D environment. In the past few decades, a multitude of digital models have been developed to facilitate complex spatial learning of the human body. However, there is limited empirical evidence to guide the development and integration of effective computer models for teaching and learning. The purpose of this article is to describe the development of a dynamic head and neck model with flexible displays (2D, 3D, and stereoscopic 3D) and interactive control features that can be later used to design and test the efficacy of computer models as a means of improving student learning. The model was created using computer tomography scans of a human cadaver. Anatomical structures captured on the scans were segmented into discreet areas, and then reconstructed in three‐dimensions using specialized software. The final model consists of 70 distinct anatomical structures that can be displayed in 2D, 3D, or stereoscopic 3D. In 3D mode, a mouse can be used to actively and continuously interact with the model by manipulating viewer orientation, altering surface transparency, superimposing 2D scans with 3D reconstructions, removing or adding structures sequentially, and customizing animated scenes to show complex anatomical pathways or relationships. Anat Sci Educ 2: 294–301, 2009. © 2009 American Association of Anatomists. 相似文献
17.
以焦炉为例,介绍了一种复杂设备的三维结构交互式演示系统开发方法。应用SketchUp建立焦炉各组成部分的三维数字模型,并导出展示其内部结构的图片和动画。应用Authorware制作焦炉结构三维交互演示系统,该演示系统能用大量的三维图像和动画生动形象地展示焦炉各大组成部分的内部结构和基本工作原理。 相似文献
18.
针对复杂结构仿真中有限元仿真精度及效率不高的问题,提出采用高阶响应面方法进行建模及优化,并用桥梁模型来验证。选取合适参数,采用试验设计获取响应样本点,基于数理统计的逐步回归法对各自变量进行显著性分析,筛选对目标响应函数显著度高的自变量,再应用最小二乘法拟合各自变量的系数,得到三阶多项式响应面模型,用多目标优化算法进行优化。对比修正前后模态频率,结果表明应用响应面方法能得到简单而高精度的结构模型,从而验证了高阶响应面方法在建模及模型优化中的有效性。 相似文献
19.
Prediction of channel dredging volume is critical for project cost estimation. However, many proposed approximate methods are not accurate. This paper presents a novel numerical method to accurately calculate the dredg- ing volume using a 3D stratum model (DSM) and a channel surface model. First, the 3D DSM is constructed rapidly yet accurately from non-uniform rational B-splines (NURBS) surfaces through Boolean operation between a physical terrain model and a stratum surfaces model. Then, a parametric channel surface model is built from cross-section data and a channel center line using code implemented in the VC++ programming language. Finally, the volumes of different types of physical stratums can be calculated automatically and hierarchically to determine the dredging volume. Practical application shows that the DSM method is more precise and faster compared to the section method, and that the implementation of the developed software provides an interactive graphical user interface and visual presentation. 相似文献
20.
An automatic generation method of geological cross-sections in dredging engineering based on 3D geological solid models is presented.The 3D geological models are built applying the non-uniform rational B-splines(NURBS) technique,and a 2D profile can be calculated and generated automatically through Boolean operation to meet the demands of dredging projects.Moreover,an automatic marking method for geological attributes is put forward based on database technology,and the geological attributes include the profile name,scale,horizontal and vertical relative coordinates,geological lithology,and 2D standard lithology legend.At the same time,the automatic marking method can also provide an interactive mode for geological engineers to edit and modify the profile in the modeling system.Practical engineering applications show that the automatic generation method is a simple,flexible,fast and precise visual graphics rendering process that can create 2D standard profiles automatically and efficiently.This method also provides a convenient support tool for geological engineering digital analysis. 相似文献