森林场景可视化和林火模拟仿真技术研究综述

森林是生态环境系统的重要组成部分。随着气候变暖,恶劣气候气象条件造成全球森林火灾频繁发生,给国民经济和消防救援带来巨大挑战,森林火灾已成为全球主要的自然灾害。因此,森林场景可视化建模、3维场景仿真、林火模拟仿真、火场复现、预测和灾害评估成为林业虚拟仿真研究热点。本文对树木形态结构建模技术、森林场景大规模重建和实时渲染、森林场景可视化、林火模型和林火模拟仿真等前沿技术和算法进行综述。对相关的林木、植被的形态结构表达和真实感可视化建模方法进行归纳分类,并对不同可视化方法的算法优劣、复杂度、实时渲染效率和适用场景进行讨论。基于规则的林木建模方法和基于林分特征的真实场景重建方法对大规模森林场景重建技术进行分类,基于物理模型、经验模型和半经验模型对森林火灾的林火模型、单木林火、多木林火模拟和蔓延进行总结,对影响林火蔓延的不同环境气象因子（如地形地貌、湿度、可燃物等）和森林分布对林火发生、扩散和蔓延的影响进行分析,对不同算法的优劣进行对比、分析和讨论,对森林场景可视化和林火模拟仿真技术未来的发展方向、存在问题和挑战进行展望。本文为基于森林真实场景的森林火灾模拟仿真和数字孪生沉浸式互动模拟系统的构建提供了理论方法基础,该平台可以实现森林场景快速构建、不同火源林火模拟、火场蔓延模拟仿真以及不同气象影响条件的火场预测,可对森林火场救援指挥、火场灾害评估和火场复原提供可视化决策支持。     

Deep learning-based smart task assistance in wearable augmented reality

Wearable augmented reality (AR) smart glasses have been utilized in various applications such as training, maintenance, and collaboration. However, most previous research on wearable AR technology did not effectively supported situation-aware task assistance because of AR marker-based static visualization and registration. In this study, a smart and user-centric task assistance method is proposed, which combines deep learning-based object detection and instance segmentation with wearable AR technology to provide more effective visual guidance with less cognitive load. In particular, instance segmentation using the Mask R-CNN and markerless AR are combined to overlay the 3D spatial mapping of an actual object onto its surrounding real environment. In addition, 3D spatial information with instance segmentation is used to provide 3D task guidance and navigation, which helps the user to more easily identify and understand physical objects while moving around in the physical environment. Furthermore, 2.5D or 3D replicas support the 3D annotation and collaboration between different workers without predefined 3D models. Therefore, the user can perform more realistic manufacturing tasks in dynamic environments. To verify the usability and usefulness of the proposed method, we performed quantitative and qualitative analyses by conducting two user studies: 1) matching a virtual object to a real object in a real environment, and 2) performing a realistic task, that is, the maintenance and inspection of a 3D printer. We also implemented several viable applications supporting task assistance using the proposed deep learning-based task assistance in wearable AR.     

A streaming-based solution for remote visualization of 3D graphics on mobile devices

Mobile devices such as personal digital assistants, tablet PCs, and cellular phones have greatly enhanced user capability to connect to remote resources. Although a large set of applications is now available bridging the gap between desktop and mobile devices, visualization of complex 3D models is still a task hard to accomplish without specialized hardware. This paper proposes a system where a cluster of PCs, equipped with accelerated graphics cards managed by the Chromium software, is able to handle remote visualization sessions based on MPEG video streaming involving complex 3D models. The proposed framework allows mobile devices such as smart phones, personal digital assistants (PDAs), and tablet PCs to visualize objects consisting of millions of textured polygons and voxels at a frame rate of 30 fps or more depending on hardware resources at the server side and on multimedia capabilities at the client side. The server is able to concurrently manage multiple clients computing a video stream for each one; resolution and quality of each stream is tailored according to screen resolution and bandwidth of the client. The paper investigates in depth issues related to latency time, bit rate and quality of the generated stream, screen resolutions, as well as frames per second displayed     

基于网格的Web可视化系统设计与实现

面向网格的数据可视化共享地理分布的数据源、分析设备、可视化设备等，提供透明访问能力。基于网格开发了一个Web可视化系统，分为3层：Web页面，Web服务器，可视化服务器。通过JSP为可视化用户提供Web访问界面，内嵌的VisPortal提供网格访问门户；Web服务器通过Portal服务器管理、调度、使用网格资源，协调用户与网格资源之间的交互；基于Vis5D构建的可视化服务器作为网格资源，实现对数值天气模型产生的5-D网格数据集的可视化。     

基于SolidWorks 的可视化定制研究

针对可视化定制系统中如何实时自动装配和交互浏览的问题,提出一种基于 SolidWorks 二次开发自动装配的方法。用户在网页上确定定制方案后,服务器端和与服务器有 固定联系的一台主机远程通讯,对SolidWorks 二次开发后的自动装配程序安装在此主机上,服 务器端远程启动主机上的自动装配程序,并接收装配完整的eDrawings 文件,将三维模型反馈 到网页上显示,用户可以在网页上实现虚拟交互浏览。该方法可以实现三维模型在多选择方案 下的实时自动组装和网页上的虚拟交互。     

Task-specific visualization design

This case study in operational weather forecasting demonstrates the principles of task-specific visualization design: defining user needs, implementing that definition, and establishing techniques for different user goals. The current applications can generate visualizations for the Web after an intermediate step of migrating the products to a Web server. This proves advantageous in an operational environment because the forecaster has content control. However, direct generation within a Web browser, which requires a simplified user interface and content, will require further refinement of the task decomposition. The notion of task-driven customization of content and interface has succeeded in weather forecasting, but the idea also applies to other domains. The potential benefits should encourage visualization designers to adopt these principles in their application development     

三维可视化技术在数字林业中的应用研究

数字林业的三维可视化是在林学和计算机图形学领域研究的一个热点,从简单的林木三维建模到辅助进行森林空间结构合理化,三维可视化技术都提供了全新的森林经营理念和生产管理方式。从树木模型、虚拟林相图、生长模型、林火模拟、病虫害监测、森林空间结构六个方面介绍了三维可视化技术在数字林业中的应用概况,并且分析了三维可视化技术对林业生产、经营、管理、决策等起到的重要作用。森林资源信息量大、涉及面广、关系复杂,因此森林资源三维可视化的研究还需要不断深入。     

可视化资源网格化方法

为提高可视化资源的使用效率,提出一种可视化资源网格化方法。研究网格环境下可视化资源共享的体系结构和工作模式以及可视化资源服务化封装方法。可视化服务利用帧缓存捕捉可视化程序运行屏幕并保存为图像文件,通过Web服务器传送至远程的客户端显示。用户通过客户端向可视化服务提出请求,该请求被封装为XML格式文件,包含可视化任务执行所需参数描述信息。以虚拟样机可视化虚拟环境的网格化为例,验证了该方法的有效性。     

海河流域水文预报系统软件开发

基于计算机图形技术和数据库技术，开发了一套海河流域水文预报软件系统。该系统采用客户／服务器体系结构，基础数据来源于系统远程服务器数据库，具有雨水情分析处理，洪水，水文预报信息查询，地理分布式信息查询（电子地图查询），图形显示与打印，帮助等功能，可以及时，准确地进行海河流域水文预报和信息查询，也可以图形显示分析，预测结果，用户界面友好，使用方便。     

An integrated VR–GIS navigation platform for city/region simulation

This paper introduces a virtual city oriented VR–GIS platform which synthesizes several latest information technologies including virtual reality, 3D geographical information system, remote sensing, and multi‐dimensional visualization. The platform is a seamless integration of VR functions and GIS analysis methods, which can be used to organize and present massive spatial data. It also supplies 3D spatial analysis functions, 3D visualization for spatial process and natural simulation, and serves as an engine platform for digital city. Copyright © 2009 John Wiley & Sons, Ltd.     

基于OpenGL实现真实感地形表现的研究

三维真实感图形是科学可视化、计算机动画、虚拟现实的技术核心,也是时空一体化地理信息系统的关键技术,而OpenGL又是目前最新的三维图形国际标准,为了实现地形的真实感显示,讨论了三维真实感地形表现在OpenGL支持下的地形模型映、遥感影象与地形的融合、专题信息与地形的融合、以及动画与虚拟现实等技术实现方法,并在荆江分洪区洪水演进模拟系统等开发中得到应用。     

Two 2D postprocessing tools and their applications to the improvement of 3D pictures

When displaying abstract objects, as in the case of scientific visualization, it is manadatory to give the user a maximum of cues to help him understand the displayed structures. In this short note, we describe two general, simple 2D postprocessing tools and their applications for the improvement of 3D perception by means of simulation of realistic 3D effects.     

Interactive, internet delivery of visualization via structured prerendered multiresolution imagery

We present a novel approach for latency-tolerant delivery of visualization and rendering results where client-side frame rate display performance is independent of source dataset size, image size, visualization technique or rendering complexity. Our approach delivers pre-rendered, multiresolution images to a remote user as they navigate through different viewpoints, visualization or rendering parameters. We employ demand-driven tiled, multiresolution image streaming and prefetching to efficiently utilize available bandwidth while providing the maximum resolution user can perceive from a given viewpoint. Since image data is the only input to our system, our approach is generally applicable to all visualization and graphics rendering applications capable of generating image files in an ordered fashion. In our implementation, a normal web server provides on-demand images to a remote custom client application, which uses client-pull to obtain and cache only those images required to fulfill the interaction needs. The main contributions of this work are: (1) an architecture for latency-tolerant, remote delivery of precomputed imagery suitable for use with any visualization or rendering application capable of producing images in an ordered fashion; (2) a performance study showing the impact of diverse network environments and different tunable system parameters on end-to-end system performance in terms of deliverable frames per second.     

并行应用程序的远程实时跟踪可视化系统的设计及实现

并行应用程序的远程实时跟踪可视化技术通过实现对并行应用程序的实时监控,帮助科研人员更进一步地了解和控制并行数值模拟的计算过程．介绍一个面向并行应用程序的远程实时跟踪可视化系统．该系统远程实时访问运行在分布存储并行机上的并行程序中的变量,将计算的中间结果实时地显示在客户端图形工作站上,从而实现程序的远程实时跟踪．从设计目标、体系结构及其实现等几个方面来介绍该系统,着重讲述该系统中的核心部分——数据传输模块的实现,详细阐述该模块实现过程中所采用的分布类型数据的位置索引及同步访问机制等关键技术．     

Geographic Data Capturing Technique based on Google Maps API V3

Traditional remote sensing mapping methods,which need professionals to take long time and utilize specialized software to carefully cope with a lot of local and isolated remote sensing images to get their desired information,have serious limitations.This paper presents an interactive geographic data acquisition and mapping solution,which all based on Googles global high-resolution remote sensing image and Google Maps API V3.The solution is built into an application of B/S structure.It utilizes the Google Maps API listeners to pick the latitude and longitude coordinates of the special points in landmarks’ outlines and to progressively construct their graphics with customized geographic models.It also uses Ajax technology to accomplish the data communication between browser and server, and adopts Microsoft XMLDOM methods to store and process the data in KML files.The visualization of selecting and editing KML data is performed with the help of KML layer mouse event’s properties and a temporary KML layer.The technology application has a friendly user interface and can be used to produce the large-scale street map quickly.     

VRML植被冠层光照的可视化

植被冠层是植被遥感数据的重要体现,更是利用计算机仿真手段进行数字化三维模拟的关键因素之一。本文讨论了基于植被冠层光照的理论基础,利用虚拟现实建模语言进行可视化输出,为以作物为中心的遥感数据应用提供重要理论支撑。     

虚拟情景实训环境三维模拟

应用计算机技术当中的虚拟模拟技术,对于当前各领域实现虚拟情景三维模拟训练已成为可能。本文研究当前技术环境下,利用Unity3D模拟平台构造虚拟情景训练系统的开发与设计。从三维模拟训练系统的关键技术研究入手,以三维场景优化、物理碰撞逻辑检测、动态加载场景以及网络通信作为开发的重点,设计出较为先进和逼真的虚拟情境下三维模拟训练系统。并以消防部门作为系统应用的检测部门,检测结果表示此系统可以很好的表现出现场场景的模拟程度以及逻辑,对于加强消防部门的训练技术和应用效果有很大优势。     

Streaming of Complex 3D Scenes for Remote Walkthroughs

We describe a new 3D scene streaming approach for remote walkthroughs. In a remote walkthrough, a user on a client machine interactively navigates through a scene that resides on a remote server. Our approach allows a user to walk through a remote 3D scene, without ever having to download the entire scene from the server. Our algorithm achieves this by selectively transmitting only small parts of the scene and lower quality representations of objects, based on the user's viewing parameters and the available connection bandwidth. An online optimization algorithm selects which object representations to send, based on the integral of a benefit measure along the predicted path of movement. The rendering quality at the client depends on the available bandwidth, but practical navigation of the scene is possible even when bandwidth is low.     

基于Restful的身份认证服务

利用Restful Web服务技术,设计一种身份认证服务。该服务将身份认证发布为Rest服务,供本地用户和远程用户调用,同时采用加密令牌方式将用户认证信息保存客户端的令牌中,应用服务不再使用Session保存认证用户信息,而是通过解密令牌密文获取认证用户信息,既保证用户的信息安全,又使得应用服务器具有良好的动态伸缩性。     

三维可视化技术在数字林业中的应用研究

数字林业的三维可视化是在林学和计算机图形学领域研究的一个热点,从简单的林木三维建模到辅助进行森林空间结构合理化,三维可视化技术都提供了全新的森林经营理念和生产管理方式。从树木模型、虚拟林相图、生长模型、林火模拟、病虫害监测、森林空间结构六个方面介绍了三维可视化技术在数字林业中的应用概况,并且分析了三维可视化技术对林业生产、经营、管理、决策等起到的重要作用。森林资源信息量大、涉及面广、关系复杂,因此森林资源三维可视化的研究还需要不断深入。