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1.
Virtual 3D city models increasingly cover whole city areas; hence, the perception of complex urban structures becomes increasingly difficult. Using abstract visualization, complexity of these models can be hidden where its visibility is unnecessary, while important features are maintained and highlighted for better comprehension and communication. We present a technique to automatically generalize a given virtual 3D city model consisting of building models, an infrastructure network and optional land coverage data; this technique creates several representations of increasing levels of abstraction. Using the infrastructure network, our technique groups building models and replaces them with cell blocks, while preserving local landmarks. By computing a landmark hierarchy, we reduce the set of initial landmarks in a spatially balanced manner for use in higher levels of abstraction. In four application examples, we demonstrate smooth visualization of transitions between precomputed representations; dynamic landmark highlighting according to virtual camera distance; an implementation of a cognitively enhanced route representation, and generalization lenses to combine precomputed representations in focus + context visualization. 相似文献
2.
《International journal of human-computer studies》2008,66(4):243-256
Navigation designs in virtual environments often draw on research findings on human navigation behaviors in the real world, in particular the landmark–route–survey spatial knowledge model. Geographers and cognitive psychologists have argued that this model is insufficient to capture the complexity of spatial cognition related to navigation. They have suggested that new theories are needed to understand the integration of various kinds of spatial knowledge and their relationship with spatial activities, such as route planning, route choosing and so on. In virtual environments, users can scale up and down the virtual space to obtain different spatial knowledge and interaction domains. Such flexibility offers an opportunity to deepen our understanding of the relationship between spatial knowledge and spatial action. This paper reports a study on how scaling in virtual environments can improve the integration of spatial knowledge and spatial action. This paper first proposes a multiscale progressive model that couples spatial knowledge and movement across scale in navigation in virtual environments. Then, the paper introduces the design of multiscale environments to support the coupling. Results of an experimental study show the benefits of the coupled spatial knowledge and movement for navigation involving subtasks at different scale levels. In addition to helping better understand the relationship between spatial knowledge and spatial action, this research also gives some insight into designs to support navigation in virtual environments as well as designs to support cross-scale spatial knowledge access in the real world. 相似文献
3.
根据多分辨率Reeb图(MRG)的原理,提出一种基于关节特征约束的骨架优化算法。它克服了基于曲率约束提取骨架方法中逐点计算顶点的曲率约束轮廓的低效性,通过分析网格顶点的离散高斯曲率,获取模型表面上具有凹陷特性的双曲极值点作为约束点, 进行关节特征区域的有效提取。进而增加关节特性点,优化MRG骨架。实验结果表明,本方法有效地突出了模型的拓扑分支特征以及模型表面的细节,提高了骨架提取的精度和效率。 相似文献
4.
Daniel Ribeiro Trindade Alberto Barbosa Raposo 《Multimedia Tools and Applications》2014,73(2):939-959
Navigation in virtual 3D environments, especially those with multiscale features, is still a problem for many users. In this regard, a good design of the navigation interfaces is critical to ensure that the users navigate with the best possible efficiency and comfort. In this paper, we present improvements for two well-known interfaces: fly, including support to collision treatment and automatic navigation speed adjustment in relation to scale, and examine, with automatic pivot point. Such techniques are based on the cubemap structure, which provides information about the surrounding environment at each instant. Usability tests with both beginner and advanced users revealed that the proposed techniques created a significant improvement in the execution of navigation tasks and a reduction in navigation errors. 相似文献
5.
三维虚拟漫游技术的研究 总被引:4,自引:0,他引:4
三维虚拟现实漫游技术目前是国内外的研究热点之一.主要研究和探讨了利用五点定位LOD四又树组织和管理大规模地形数据,并以井地算法实现大规模地形实时渲染,能有效地提升三维场景的渲染速度.提出了一种基于场景投影图矩阵的自动漫游路径生成的钢丝算法,该算法适用于各种复杂的三维虚拟场景并能生成光滑的自动漫游路径. 相似文献
6.
How to achieve consistency for 3D city models 总被引:1,自引:1,他引:0
Consistency is a crucial prerequisite for a large number of relevant applications of 3D city models, which have become more
and more important in GIS. Users need efficient and reliable consistency checking tools in order to be able to assess the
suitability of spatial data for their applications. In this paper we provide the theoretical foundations for such tools by
defining an axiomatic characterization of 3D city models. These axioms are effective and efficiently supported by recent spatial
database management systems and methods of Computational Geometry or Computer Graphics. They are equivalent to the topological
concept of the 3D city model presented in this paper, thereby guaranteeing the reliability of the method. Hence, each error
is detected by the axioms, and each violation of the axioms is in fact an error. This property, which is proven formally,
is not guaranteed by existing approaches. The efficiency of the method stems from its locality: in most cases, consistency
checks can safely be restricted to single components, which are defined topologically. We show how a 3D city model can be
decomposed into such components which are either topologically equivalent to a disk, a sphere, or a torus, enabling the modeling
of the terrain, of buildings and other constructions, and of bridges and tunnels, which are handles from a mathematical point
of view. This enables a modular design of the axioms by defining axioms for each topological component and for the aggregation
of the components. Finally, a sound, consistent concept for aggregating features, i.e. semantical objects like buildings or
rooms, to complex features is presented. 相似文献
7.
Multiscale multigrid (MSMG) method is an effective computational framework for efficiently computing high accuracy solutions for elliptic partial differential equations. In the current MSMG method, compared to the CPU cost on computing sixth-order solutions by applying extrapolation and other techniques on two fourth-order solutions from different scales grids, much more CPU time is spent on computing fourth-order solutions themselves on coarse and fine grids, particularly for high-dimensional problems. Here we propose to embed extrapolation cascadic multigrid (EXCMG) method into the MSMG framework to accelerate the whole process. Numerical results on 3D Poisson equations show that the new EXCMG–MSMG method is more efficient than the existing MSMG method and the EXCMG method for sixth-order solution computation. 相似文献
8.
Elevation datasets (e.g. point clouds) are an essential but often unavailable ingredient for the construction of 3D city models. We investigate in this paper to what extent can 3D city models be generated solely from 2D data without elevation measurements. We show that it is possible to predict the height of buildings from 2D data (their footprints and attributes available in volunteered geoinformation and cadastre), and then extrude their footprints to obtain 3D models suitable for a multitude of applications. The predictions have been carried out with machine learning techniques (random forests) using 10 different attributes and their combinations, which mirror different scenarios of completeness of real-world data. Some of the scenarios resulted in surprisingly good performance (given the circumstances): we have achieved a mean absolute error of 0.8m in the inferred heights, which satisfies the accuracy recommendations of CityGML for LOD1 models and the needs of several GIS analyses. We show that our method can be used in practice to generate 3D city models where there are no elevation data, and to supplement existing datasets with 3D models of newly constructed buildings to facilitate rapid update and maintenance of data. 相似文献
9.
Studies have suggested that there is farming potential in urban residential buildings. However, these studies are limited in scope, require field visits and time-consuming measurements. Furthermore, they have not suggested ways to identify suitable sites on a larger scale let alone means of surveying numerous micro-locations across the same building. Using a case study area focused on high-rise buildings in Singapore, this paper examines a novel application of three-dimensional (3D) city models to identify suitable farming micro-locations (level and orientation) in residential buildings. We specifically investigate whether the vertical spaces of these buildings comprising outdoor corridors, façades and windows receive sufficient photosynthetically active radiation (PAR) for growing food crops and do so at a high resolution. We also analyze the spatio-temporal characteristics of PAR, and the impact of shadows and different weather conditions on PAR in the building. Environmental simulations on the 3D model of the study area indicated that the cumulative daily PAR or Daily Light Integral (DLI) at a location in the building was dependent on its orientation and shape, sun's diurnal and annual motion, weather conditions, and shadowing effects of the building's own façades and surrounding buildings. The DLI in the study area generally increased with building's levels and, depending on the particular micro-location, was found suitable for growing moderately light-demanding crops such as lettuce and sweet pepper. These variations in DLI at different locations of the same building affirmed the need for such simulations. The simulations were validated with field measurements of PAR, and correlation coefficients between them exceeded 0.5 in most cases thus, making a case that 3D city models offer a promising practical solution to identifying suitable farming locations in residential buildings, and have the potential for urban-scale applications. 相似文献
10.
Gavin Miller Eric Hoffert Shenchang Eric Chen Elizabeth Patterson Dean Blackketter Steve Rubin Sally Ann Applin Derrick Yim Jim Hanan 《Computer Animation and Virtual Worlds》1992,3(3):183-197
The Virtual Museum is an interactive, electronic museum where users can move from room to room, and select any exhibit in a room for more detailed examination. The exhibits in the museum are educational, encompassing topics such as medicine, plant growth, the environment, and space. To facilitate interaction with the museum, a new method for navigating through a prerendered 3D space, and interacting with objects in that space has been developed, called ‘virtual navigation’. Virtual navigation employs real-time video decompression for the display of, and interaction with, high-quality computer animation. In addition, a representation for 3D objects in animated sequences is used which permits pixel-accurate, frame-accurate object picking, so that a viewer can select any 3D object to trigger movement within the 3D space, to examine an exhibit in animated form, or to play a digital movie or soundtrack. The use of precomputed video permits 3D navigation in a realistic-looking space, without requiring special-purpose graphics hardware. 相似文献
11.
《Robotics and Autonomous Systems》2014,62(12):1806-1815
This paper deals with the navigation in formation of a group of mobile robots. A set of virtual targets (points) forms a virtual structure of the same shape as the desired formation. Hence, to join and to remain in this formation, each robot has only to track one of these targets. In order to track the chosen target, it has to be attainable by the robot despite its kinematic constraints. This paper studies then the maximum allowed dynamic of the virtual structure according to the kinematic constraints of the robots. Both linear and angular velocities of the targets are constrained. Moreover, depending on these velocities, some relative positions (targets) in the formation become unattainable. These positions are also defined. A stable control law allows us to attain the generated set-points. Simulation and experimental results validate the proposed contributions. 相似文献
12.
Barneche-Naya Viviana Hernández-Ibañez Luis A. 《Universal Access in the Information Society》2021,20(3):513-529
Universal Access in the Information Society - This paper describes the results of a case study intended to compare three different user movement paradigms (metaphoric, symbolic and natural)... 相似文献
13.
Head-mounted display versus desktop for 3D navigation in virtual reality: a user study 总被引:1,自引:1,他引:0
Beatriz Sousa Santos Paulo Dias Angela Pimentel Jan-Willem Baggerman Carlos Ferreira Samuel Silva Joaquim Madeira 《Multimedia Tools and Applications》2009,41(1):161-181
Virtual Reality (VR) has been constantly evolving since its early days, and is now a fundamental technology in different application
areas. User evaluation is a crucial step in the design and development of VR systems that do respond to users’ needs, as well
as for identifying applications that indeed gain from the use of such technology. Yet, there is not much work reported concerning
usability evaluation and validation of VR systems, when compared with the traditional desktop setup. The paper presents a
user study performed, as a first step, for the evaluation of a low-cost VR system using a Head-Mounted Display (HMD). That
system was compared to a traditional desktop setup through an experiment that assessed user performance, when carrying out
navigation tasks in a game scenario for a short period. The results show that, although users were generally satisfied with
the VR system, and found the HMD interaction intuitive and natural, most performed better with the desktop setup.
相似文献
Beatriz Sousa SantosEmail: |
14.
The shapes of our cities change very frequently. These changes have to be reflected in data sets representing urban objects.
However, it must be assured that frequent updates do not affect geometric-topological consistency. This important aspect of spatial data quality guarantees essential assumptions on which users and applications of 3D city
models rely: viz. that objects do not intersect, overlap or penetrate mutually, or completely cover one another. This raises
the question how to guarantee that geometric-topological consistency is preserved when data sets are updated. Hence, there
is a certain risk that plans and decisions which are based on these data sets are erroneous and that the tremendous efforts
spent for data acquisition and updates become vain. In this paper, we solve this problem by presenting efficient transaction rules for updating 3D city models. These rules guarantee that geometric-topological consistency is preserved (Safety) and allow for the generation of arbitrary consistent 3D city models (Completeness). Safety as well as completeness is proven with mathematical rigor, guaranteeing the reliability of our method. Our method
is applicable to 3D city models, which define—besides the terrain surface—complex spatial objects like buildings with rooms
and storeys as interior structures, as well as bridges and tunnels. Those objects are represented as aggregations of solids,
and their surfaces are complex from a topology point of view. 3D GIS models like CityGML, which are widely used to represent cities, provide the means to define semantics, geometry and topology, but do not address
the problem of maintaining consistency. Hence, our approach complements CityGML. 相似文献
15.
At the different stages of the PLM, companies develop numerous checklist-based procedures involving prototype inspection and testing. Besides, techniques from CAD, 3D imaging, animation and virtual reality now form a mature set of tools for industrial applications. The work presented in this article develops a unique framework for immersive checklist-based project reviews that applies to all steps of the PLM. It combines immersive navigation in the checklist, virtual experiments when needed and multimedia update of the checklist. It provides a generic tool, independent of the considered checklist, relies on the integration of various VR tools and concepts, in a modular way, and uses an original gesture recognition. Feasibility experiments are presented, validating the benefits of the approach. 相似文献
16.
Naoki Sasaki Hsiang‐Ting Chen Daisuke Sakamoto Takeo Igarashi 《Computer Animation and Virtual Worlds》2015,26(2):185-194
We present facetons, geometric modeling primitives designed for building architectural models especially effective for a virtual environment where six degrees of freedom input devices are available. A faceton is an oriented point floating in the air and defines a plane of infinite extent passing through the point. The polygonal mesh model is constructed by taking the intersection of the planes associated with the facetons. With the simple interaction of faceton, users can easily create 3D architecture models. The faceton primitive and its interaction reduce the overhead associated with standard polygonal mesh modeling, where users have to manually specify vertexes and edges which could be far away. The faceton representation is inspired by the research on boundary representations (B‐rep) and constructive solid geometry, but it is driven by a novel adaptive bounding algorithm and is specifically designed for 3D modeling activities in an immersive virtual environment. We describe the modeling method and our current implementation. The implementation is still experimental but shows potential as a viable alternative to traditional modeling methods. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
17.
The level of detail (LOD) concept of the OGC standard CityGML 2.0 is intended to differentiate multi-scale representations of semantic 3D city models. The concept is in practice principally used to indicate the geometric detail of a model, primarily of buildings. Despite the popularity and the general acceptance of this categorisation, we argue in this paper that from a geometric point of view the five LODs are insufficient and that their specification is ambiguous.We solve these shortcomings with a better definition of LODs and their refinement. Hereby we present a refined set of 16 LODs focused on the grade of the exterior geometry of buildings, which provide a stricter specification and allow less modelling freedom. This series is a result of an exhaustive research into currently available 3D city models, production workflows, and capabilities of acquisition techniques. Our specification also includes two hybrid models that reflect common acquisition practices. The new LODs are in line with the LODs of CityGML 2.0, and are intended to supplement, rather than replace the geometric part of the current specification. While in our paper we focus on the geometric aspect of the models, our specification is compatible with different levels of semantic granularity. Furthermore, the improved LODs can be considered format-agnostic.Among other benefits, the refined specification could be useful for companies for a better definition of their product portfolios, and for researchers to specify data requirements when presenting use cases of 3D city models. We support our refined LODs with experiments, proving their uniqueness by showing that each yields a different result in a 3D spatial operation. 相似文献
18.
This article presents a classifier based on Support Vector Machines (SVMs), an advanced machine learning method for semantic
enrichment of coarse 3D city models by deriving the building type. The information on the building type (detached building,
terraced building, etc.) is essential for a variety of relevant applications of 3D city models like spatial marketing, real
estate management and marketing, and for visualization. The derivation of the building type from coarse data (mainly 2D footprints,
building heights and functions) seems impossible at first sight. However it succeeds by incorporating the spatial context
of a building. Since the input data can be derived easily and at very low cost, this method is widely applicable. Nevertheless,
as with all supervised learning algorithms, obtaining labelled training data is very time-consuming. Herewith, we provide
a method which uses outlier detection and clustering methods to support users in efficiently and rapidly obtaining adequate
training data. 相似文献
19.
20.
Network-based visualization of 3D landscapes and city models. 总被引:1,自引:0,他引:1
Jér?me Royan Patrick Gioia Romain Cavagna Christian Bouville 《Computer Graphics and Applications, IEEE》2007,27(6):70-79
To improve the visualization of large 3D landscapes and city models in a network environment, the authors use two different types of hierarchical level-of-detail models for terrain and groups of buildings. They also leverage the models to implement progressive streaming in both client-server and peer-to-peer network architectures. 相似文献