基于联锁分块的大规模地形建模方法研究

针对已有MRLoD算法生成的地形=三角形网不稳定等缺点,提出了一种新的基于联锁分块的大规模地形建模方法,在对地形进行分块调度的基础上通过预先建立分块模板和分块联锁模板,渲染时动态匹配各模板建立平滑完整的分块模型,在分块调度及附加计算策略下,拼接各分块以完成整块地形的多分辨率建模,并以高效的方式将模型数据传人渲染硬件.实验表明,在满足了精度要求的同时提高了模型的稳定性,有效减少了实时计算量,在渲染效率上取得了令人满意的结果,能够满足用户对大规模地形的实时漫游的要求.     

一种视相关的网格简化方法*

针对网格模型的实时显示问题提出了一种视相关的网格简化方法。在网格简化中,将影响图形对象重要性的视觉敏感度与图形对象在屏幕上投影面积两者有效结合,实现网格模型的实时大幅度简化, 实验结果表明,简化速度快,但显示并无明显失真。     

古木建筑裂缝多LoD表达与信息自动集成

古木建筑具有极高的价值,科学认识其损伤现状,并对损伤进行直观表达与信息 自动集成,有利于更好地进行文化传承。尽管建筑遗产信息模型(HBIM)技术具有模型与信息高 度关联的特点,可将信息整合至模型中,与古建筑信息表达集成需求高度契合,但在应用方面 仍存在部分难题,如损伤模型表达精细度划分,损伤信息量庞大难以快速集成。本文以古木建 筑裂缝损伤为例,首先建议了裂缝模型多细节层次(LoD)表达标准;然后分析了 HBIM 的信息 集成方式,其在 Revit 软件中以电子列表方式管理构件信息;为解决信息量大的难题,对软件 进行二次开发编写外部命令,加载成为外部应用实现信息自动集成更新;最后以一古木建筑 HBIM 模型进行方法验证,4 s 内完成了 64 根柱子的信息自动化集成。表明了裂缝多 LoD 表达 方法与信息自动集成算法的高效性与可靠性,可为历史建筑信息的表达、集成与管理提供方法 借鉴。     

基于显著几何特征的古木建筑关键构件 多LoD尺寸信息提取方法

摘 要：古木建筑关键构件的尺寸信息是其安全性能评估与提升、历史文化传承的重要基 础,然而该信息的提取尚缺乏高效、高精度的方法。三维激光扫描的精细测绘技术为该问题的 解决提供了科学手段,但点云数据体量庞大,无法直接获取尺寸信息。针对尺寸信息的多细节 层级(LoD)特性,提出了多 LoD 模型标准,建议了相应的显著几何特征参数。结合高保真点云 数据,系统地提出了一套基于点云数据的关键构件多 LoD 尺寸信息自动化提取方法,可准确、 高效地提取多 LoD 尺寸信息。对典型关键构件进行了多 LoD 尺寸信息提取,该方法可在 7 min 内完成百万级点云数据的信息提取,且尺寸相对误差不超过 2%,绝对误差绝大部分小于 0.5 mm,验证了该方法的高效性和可靠性。     

多边形网格模型简化算法综述

系统介绍了多边形网格模型简化算法,给出了基本术语和算法分类,在此基础上对各种算法的优缺点进行了分析,然后根据误差控制、简化速度等指标对各种算法进行了对比,并对简化算法的选择给出了相应的建议,最后对简化算法在产品异地协同设计中的应用以及深层次问题进行了探讨.     

基于边折叠的网格简化算法研究

在计算机图形学和几何造型中,物体表面常用多边形网格模型来描述.一个复杂的场景可能会包含大量的多边形,不利于存储、传输及绘制.网格简化技术用于处理计算机图形学领域中广泛使用的多边形网格数据,主要应用领域有科学可视化、实时显示和虚拟现实等.文章给出了网格简化方法的分类,研究了基于边折叠的简化算法,对相关技术及其特点进行了介...     

智慧BIM乔木模型：从设计图纸到施工 现场

现有的BIM应用软件提供的乔木模型多为RPC或高精度3D模型等3D CAD类型。这些模型着重于表达美感或进行展示,无法反映根系情况。虽然可能包含一定附加属性,但表达乔木生长和空间需求的功能有限。因而,冲突检查、工序调度等BIM的优势功能无从应用。风景园林实践领域已就此问题开始构建自己的模型库,但能够准确反映现状树木真实尺寸体量,以及现状树木和规划树木未来空间需求的模型仍未广泛出现。提出一种基于树冠、树干和根系构型与生长功能的实体/网面封装建模方法构建BIM乔木模型。模型形态通过一组参数调整,并根据树龄和反映环境限制因子的值来反映其变化。所包含的数据和参数数量随后期设计阶段所需的LoD(详细层级)及专业实践的具体要求而增加。该模型可以与提供本地区内外苗木商品信息的植物数据库连接使用。     

Debris Flow Simulation-Oriented Three-Dimensional Scenery Modeling and Rendering

3D (three-dimensional) process simulation is currently one of the most challenging fields of research on debris flow.Large scale terrain rendering is the most basic task of 3D scenery construction in debris flow simulation. As the major trigger for debris flow, rainfall will substantially enhance the realistic sense. Terrain and rainfall rendering in 3D debris flow simulations poses great challenges for numerical computation and graphical processing capability. In this paper, we propose to integrate GPU technology, LoD algorithms, and particle systems to realize 3D scenery modeling and rendering. The real-time LoD-based terrain modeling and rendering algorithm is presented first, and then a particle systcm-basext rainfall scenery rendering method is implemented. Experimental results demonstrate that the 3D scenery rendered with the proposed approach exhibits sound performance and fair visual effects, which lays a solid foundation for the whole process simulation of debris flow disasters.     

Towards the generation of 3D OpenStreetMap building models from single contributed photographs

3D city models are valuable and useful for many experts using this information for a wide array of environmental and sustainable analyses and services. To produce 3D city models, conventional production processes are typically conducted by authoritative mapping agencies, which mostly rely on aerial photogrammetry and laser scanning. Consequently, obtaining public domain 3D city models is challenging and limited, where the majority of open data is collected and mapped by participatory mapping driven communities. These are still limited to 2D data collection proficiencies due to the used mapping infrastructures and technological limitations. Thus, the 3rd (height) dimension is mostly missing from these maps and models, resulting in the fact that public domain 3D city models are still limited, and only scarcely used for environmental applications. Perhaps one of the most important features in 3D city models are the buildings, since they serve as a major geospatial element in many environmental applications. Our objective is to use a single contributed photograph and OpenStreetMap vector data to precisely calculate the photographed building height, and add this data to the OpenStreetMap map to enable the creation of open source Level of Detail 1 (LoD1) city models. To this end, we have developed a Newton's-based method in optimization to accurately calculate building heights from single contributed photographs taken by citizens using smartphones or tablets. An Android app, OpenStreetHeight, is developed to carry out the experiments. Based on the various medium-height buildings that were photographed using the app and processed using the developed algorithms we received accurate building height values. When compared to reliable reference field measurements, the average height mean absolute error was 30 cm. Combined with the OpenStreetMap footprint vector data, we were able to produce an average LoD1 volume mean absolute error of less than 5%, satisfying the CityGML standard quality. This research presents a framework for a semi-automatic crowdsourced user-generated content calculation of OpenStreetMap building heights, and the creation of reliable and accurate LoD1 building models, as a first step to enhance the already established 2D OpenStreetMap map infrastructure to the 3D domain. This enables expanding the use of OpenStreetMap as a comprehensive and detailed representation of our urban environment for various environmental and sustainable applications and analyses.     

一种新的多分辨率模型表示方法

提出了一种简洁高效的多分辨率模型表示方法MRM,该方法能对网格简化或精化过程进行编码,并在此基础上实现了一个多分辨率造型与编辑系统。该系统能为给定的模型生成多分辨率表示,并支持对模型的分辨率进行编辑,统一地完成有选择地精化和简化操作。