Abstract representations for interactive visualization of virtual 3D city models

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.     

Distance visualization for interactive 3D implant planning

An instant and quantitative assessment of spatial distances between two objects plays an important role in interactive applications such as virtual model assembly, medical operation planning, or computational steering. While some research has been done on the development of distance-based measures between two objects, only very few attempts have been reported to visualize such measures in interactive scenarios. In this paper we present two different approaches for this purpose, and we investigate the effectiveness of these approaches for intuitive 3D implant positioning in a medical operation planning system. The first approach uses cylindrical glyphs to depict distances, which smoothly adapt their shape and color to changing distances when the objects are moved. This approach computes distances directly on the polygonal object representations by means of ray/triangle mesh intersection. The second approach introduces a set of slices as additional geometric structures, and uses color coding on surfaces to indicate distances. This approach obtains distances from a precomputed distance field of each object. The major findings of the performed user study indicate that a visualization that can facilitate an instant and quantitative analysis of distances between two objects in interactive 3D scenarios is demanding, yet can be achieved by including additional monocular cues into the visualization.     

New paradigms for interactive 3D volume segmentation

We present a new virtual reality‐based interaction metaphor for semi‐automatic segmentation of medical 3D volume data. The mouse‐based, manual initialization of deformable surfaces in 3D represents a major bottleneck in interactive segmentation. In our multi‐modal system we enhance this process with additional sensory feedback. A 3D haptic device is used to extract the centreline of a tubular structure. Based on the obtained path a cylinder with varying diameter is generated, which in turn is used as the initial guess for a deformable surface. Copyright © 2002 John Wiley & Sons, Ltd.     

A particle system for interactive visualization of 3D flows

We present a particle system for interactive visualization of steady 3D flow fields on uniform grids. For the amount of particles we target, particle integration needs to be accelerated and the transfer of these sets for rendering must be avoided. To fulfill these requirements, we exploit features of recent graphics accelerators to advect particles in the graphics processing unit (GPU), saving particle positions in graphics memory, and then sending these positions through the GPU again to obtain images in the frame buffer. This approach allows for interactive streaming and rendering of millions of particles and it enables virtual exploration of high resolution fields in a way similar to real-world experiments. The ability to display the dynamics of large particle sets using visualization options like shaded points or oriented texture splats provides an effective means for visual flow analysis that is far beyond existing solutions. For each particle, flow quantities like vorticity magnitude and A2 are computed and displayed. Built upon a previously published GPU implementation of a sorting network, visibility sorting of transparent particles is implemented. To provide additional visual cues, the GPU constructs and displays visualization geometry like particle lines and stream ribbons.     

Consistent segmentation of 3D models

This paper proposes a method to segment a set of models consistently. The method simultaneously segments models and creates correspondences between segments. First, a graph is constructed whose nodes represent the faces of every mesh, and whose edges connect adjacent faces within a mesh and corresponding faces in different meshes. Second, a consistent segmentation is created by clustering this graph, allowing for outlier segments that are not present in every mesh. The method is demonstrated for several classes of objects and used for two applications: symmetric segmentation and segmentation transfer.     

Inside-reachable and see-through augmented reality Shell for 3D visualization and tangible interaction

Multimedia Tools and Applications - Augmented reality (AR) is considered as one of the most essential technologies for providing 3D information visualization superimposed in the physical object....     

A 3D GIS-based interactive registration mechanism for outdoor augmented reality system

Registering virtual objects with reference to their corresponding real-world objects plays a key role in augmented reality (AR) system. Although there have been a lot of work on using vision-based method to perform registration for indoor AR system, it is very difficult to apply such registration method for outdoor AR system due to the inability to modify the objects in outdoor environment and the huge range of working area. 3D Geographic Information System (GIS) is capable of providing an outdoor virtual geographic environment where users are located at, which may provide users with a corresponding virtual object for the one in the physical world. In this study, a 3D GIS-based registration mechanism is proposed for outdoor AR system. Specifically, an easy-use interactive method for precise registration was developed to improve the performance of the registration. To implement the registration mechanism, an outdoor AR system built upon 3D GIS was developed, named Augmented Reality Geographical Information System (ARGIS). ARGIS has the capability of performing precise registration in outdoor environment without using traditional vision tracking method, which thus enables users to arbitrarily manipulate the system. A prototype was developed to conduct experiment on the campus of Peking University, Beijing, China to test the proposed registration mechanism. The experiment shows that the developed registration mechanism is feasible and efficient in the outdoor environment. The ARGIS is expected to enrich the applications of outdoor AR system, including but not limited to underground facility mapping, emergency rescue and urban planning.     

Smart Vidente: advances in mobile augmented reality for interactive visualization of underground infrastructure

Many civil engineering tasks require to access geospatial data in the field and reference the stored information to the real-world situation. Augmented reality (AR), which interactively overlays 3D graphical content directly over a view of the world, can be a useful tool to visualize but also create, edit and update geospatial data representing real-world artifacts. We present research results on the next-generation field information system for companies relying on geospatial data, providing mobile workforces with capabilities for on-site inspection and planning, data capture and as-built surveying. To achieve this aim, we used mobile AR technology for on-site surveying of geometric and semantic attributes of geospatial 3D models on the user’s handheld device. The interactive 3D visualizations automatically generated from production databases provide immediate visual feedback for many tasks and lead to a round-trip workflow where planned data are used as a basis for as-built surveying through manipulation of the planned data. Classically, surveying of geospatial objects is a typical scenario performed from utility companies on a daily basis. We demonstrate a mobile AR system that is capable of these operations and present first field trials with expert end users from utility companies. Our initial results show that the workflows of planning and surveying of geospatial objects benefit from our AR approach.     

Graph-cut based interactive segmentation of 3D materials-science images

Segmenting materials’ images is a laborious and time-consuming process, and automatic image segmentation algorithms usually contain imperfections and errors. Interactive segmentation is a growing topic in the areas of image processing and computer vision, which seeks to find a balance between fully automatic methods and fully-manual segmentation processes. By allowing minimal and simplistic interaction from the user in an otherwise automatic algorithm, interactive segmentation is able to simultaneously reduce the time taken to segment an image while achieving better segmentation results. Given the specialized structure of materials’ images and level of segmentation quality required, we show an interactive segmentation framework for materials’ images that has three key contributions: (1) a multi-labeling approach that can handle a large number of structures while still quickly and conveniently allowing manual addition and removal of segments in real-time, (2) multiple extensions to the interactive tools which increase the simplicity of the interaction, and (3) a web interface for using the interactive tools in a client/server architecture. We show a full formulation of each of these contributions and example results from their application.     

基于OpenGL的三维可视化以及交互裁剪应用

通过对于医学图像可视化方法的研究,实现基于GLSL的带有交互裁剪等多种功能的三维纹理体绘制应用。该应用能使医生更加方便地观察医学图像数据内部结构,同时将多平面显示结果与体绘制结果合并显示以方便医生在观测到具体位置时获得更好的细节信息。实验结果表明：所实现应用可以对常见医学图像序列进行三维可视化并可以交互显示内部细节,交互性能好,切割速度快,效果逼真。     

Automatic upright orientation and good view recognition for 3D man-made models

Many graphics applications require that 3D models automatically be presented upright and from a good view. We propose a method that simultaneously recognizes upright orientation and good view for 3D man-made models. The strategy is to determine the best base on which a 3D model can stand upright from a small set of candidate bases. Every candidate base is composed of clustered facets of the simplified convex hull of the given 3D model. Next, a proposed UV-measurement selects the best base from the candidate bases using weighted feature-based evaluation functions based on geometrical, physical, and visual aspects. Our method has been tested using a public 3D model database and compared with previous methods. As experimental results show, our method outperforms previous work in both efficiency and accuracy.     

面向道路工程Web3D档案管理的三维可视化方法

道路工程Web3D档案管理技术对辅助提高决策能力具有重要意义。对其中的海量数据组织管理、三维整体建模及模型简化方法进行了研究。提出了基于有向无环图的三维场景组织管理方法,深度方向从总体到细节的逐步细分,广度方向按里程分段或模型类型进行划分,标准模型节点为多个父节点所共享;基于约束Delaunay三角网建立了道路三维整体模型;提出了顾及约束的三维模型简化误差度量准则,考虑了对任意边进行简化时的几何误差,并为约束边建立了一个附加误差项,保证约束边尽早细化。基于上述方法开发了道路工程Web3D档案管理系统,远程客户端可快速重构出三维模型并较好地保留了约束边,目前已应用在多条高速公路的建设、运营管理中。     

Adaptive voxels: interactive rendering of massive 3D models

We present a novel approach for interactive rendering of massive 3D models. Our approach integrates adaptive sampling-based simplification, visibility culling, out-of-core data management and level-of-detail. We use a unified scene graph representation for acceleration techniques. In preprocessing, we subdivide large objects, and build a BVH clustering hierarchy. We make use of a novel adaptive sampling method to generate LOD models: AdaptiveVoxels. The AdaptiveVoxels reduces the preprocessing cost and our out-of-core rendering algorithm improves rendering efficiency. We have implemented our algorithm on a desktop PC. We can render massive CAD and isosurface models, consisting of hundreds of millions of triangles interactively with little loss in image quality.     

A tool for the interactive 3D visualization of electronic structure in molecules and solids

This paper presents the Vienna ab initio simulation package (VASP) data viewer, a desktop 3D visualization application for the analysis of valence electronic structure information derived from first-principles quantum-mechanical density functional calculations. This tool allows a scientist to directly view and manipulate the calculated charge density or electron localization function (ELF) from an electronic structure calculation, providing insight into the nature of chemical bonding. Particular attention was given to the design and implementation of the user interface (UI) for the data viewer. It provides for expert and novice usage, and both natural direct manipulation and precise numerical control. The data viewer has proven useful to chemical scientists for understanding the results of electronic structure calculations.     

A novel progressive modelling algorithm for 3D models

This paper presents a novel progressive modelling algorithm for 3D models to generate progressive meshes. We propose a forest clustering simplification method to generate a progressive mesh of a model with the efficient and smooth transitions between meshes at different resolutions. Our approach can also integrate and balance the appearance attributes to preserve features of a model in the simplification process. We have applied our progressive modelling technique to several different kinds of input models and results show that our approach only generates efficient and smooth progressive meshes of a given model, but also preserves the features. The proposed method is very suitable for progressive transmission and real‐time rendering of 3D models in networked virtual environments. Copyright © 2002 John Wiley & Sons, Ltd.     

Lightweighting for Web3D visualization of large-scale BIM scenes in real-time

As a result of informatization in construction, Building Information Modeling (BIM) has now become a core technology for smart construction. We present a Web3D-based lightweighting solution for real-time visualization of large-scale BIM scenes, considering the redundancy, semantics, and the parameterization of BIM data under the limited resources of network bandwidth and web browsers. Taking the Industry Foundation Classes (IFC) as the input data format, we firstly conduct a semantics-guided lightweighting operation on the raw BIM scenes by removing the repetitive objects and parameterizing the swept surfaces. Secondly, we extract the exterior products from the raw BIM buildings for visibility culling and construct a Double-Layered Sparse Voxel (DLSV) index based on sparse voxelization. Thirdly, we integrate the above two together into a new data structure named Incremental Frustum of Interest (I-FOI) to manage the scene data in real-time. Our experiments demonstrate that: (1) with the semantics information, our method is able to significantly reduce the redundancy of raw large-scale BIM scenes; (2) the DLSV structure supports progressive data loading and facilitates the indoor/outdoor visibility culling efficiently; and (3) the I-FOI introduces a frustum incremental-driven mechanism into progressive data loading or unloading to improve the efficiency of resource consumption.     

Network-based visualization of 3D landscapes and city models.

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.