Matthias Trapp

Interactive Visualization of Generalized Virtual 3D City Models using Level-of-Abstraction Transitions

Virtual 3D city models play an important role in the communication of complex geospatial information in a growing number of applications, such as urban planning, navigation, tourist information, and disaster management. In general, homogeneous graphic styles are used for visualization. For instance, photorealism is suitable for detailed presentations, and non‐photorealism or abstract stylization is used to facilitate guidance of a viewers gaze to prioritized information. However, to adapt visualization to different contexts and contents and to support saliency‐guided visualization based on user interaction or dynamically changing thematic information, a combination of different graphic styles is necessary. Design and implementation of such combined graphic styles pose a number of challenges, specifically from the perspective of real‐time 3D visualization. In this paper, the authors present a concept and an implementation of a system that enables different presentation styles, their seamless integration within a single view, and parametrized transitions between them, which are defined according to tasks, camera view, and image resolution. The paper outlines potential usage scenarios and application fields together with a performance evaluation of the implementation.

3D Generalization Lenses for Interactive Focus + Context Visualization of Virtual City Models

Focus + context visualization facilitates the exploration of complex information spaces. This paper proposes 3D generalization lenses, a new visualization technique for virtual 3D city models that combines different levels of structural abstraction. In an automatic preprocessing step, we derive a generalized representation of a given city model. At runtime, this representation is combined with a full-detail representation within a single view based on one or more 3D lenses of arbitrary shape. Focus areas within lens volumes are shown in full detail while excluding less important details of the surrounding area. Our technique supports simultaneous use of multiple lenses associated with different abstraction levels, can handle overlapping and nested lenses, and provides interactive lens modification.

Towards an Indoor Level-of-Detail Model for Route Visualization

Indoor routing represents an essential feature required by applications and systems that provide spatial information about complex sites, buildings and infrastructures such as in the case of visitor guidance for trade fairs and customer navigation at airports or train stations. Apart from up-to date, precise 3D spatial models these systems and applications need user interfaces as core system components that allow users to efficiently express navigation goals and to effectively visualize routing information. For interoperable and flexible indoor routing systems, common specifications and standards for indoor structures, objects, and relationships are needed as well as for metadata such as data quality and certainty. In this paper, we introduce a classification of indoor objects and structures taking into account geometry, semantics, and appearance, and propose a level-of-detail model for them that supports the generation of effective indoor route visualization.

Interactive Multi-Perspective Views of Virtual 3D Landscape and City Models

Based on principles of panorama maps we present an interactive visualization technique that generates multi-perspective views of complex spatial environments such as virtual 3D landscape and city models. Panorama maps seamlessly combine easily readable maps in the foreground with 3D views in the background – both within a single image. Such nonlinear, non-standard 3D projections enable novel focus & context views of complex virtual spatial environments. The presented technique relies on global space deformation to model multi-perspective views while using a standard linear projection for rendering which enables single-pass processing by graphics hardware. It automatically configures the deformation in a view-dependent way to maintain the multi-perspective view in an interactive environment. The technique supports different distortion schemata beyond classical panorama maps and can seamlessly combine different visualization styles of focus and context areas. We exemplify our approach in an interactive 3D tourist information system.

Real-Time Volumetric Tests Using Layered Depth Images

This paper presents a new approach for performing efficiently 3D point-in-volume tests for solid and arbitrary complex shapes. It classifies a 3D point as inside or outside of a solid specified by 3D polygonal geometry. Our technique implements a basic functionality that offers a wide range of applications such as clipping, collision detection, interactive rendering of multiple 3D lenses as well as rendering using multiple styles. It is based on an extension of layered depth images (LDI) in combination with shader programs. An LDI contains layers of unique depth complexity and is represented by a 3D volume texture. The test algorithm transforms a 3D point into an LDI texture space and, then, performs ray marching through the depth layers to determine its classification. We show how to apply real-time volumetric tests to implement 3D clipping and rendering using multiple styles. In addition, we discuss limitations and possible improvements.

Multi-perspective 3D panoramas

This article presents multi-perspective 3D panoramas that focus on visualizing 3D geovirtual environments (3D GeoVEs) for navigation and exploration tasks. Their key element, a multi-perspective view (MPV), seamlessly combines what is seen from multiple viewpoints into a single image. This approach facilitates the presentation of information for virtual 3D city and landscape models, particularly by reducing occlusions, increasing screen-space utilization, and providing additional context within a single image. We complement MPVs with cartographic visualization techniques to stylize features according to their semantics and highlight important or prioritized information. When combined, both techniques constitute the core implementation of interactive, multi-perspective 3D panoramas. They offer a large number of effective means for visual communication of 3D spatial information, a high degree of customization with respect to cartographic design, and manifold applications in different domains. We discuss design decisions of 3D panoramas for the exploration of and navigation in 3D GeoVEs. We also discuss a preliminary user study that indicates that 3D panoramas are a promising approach for navigation systems using 3D GeoVEs.

2D and 3D presentation of spatial data: A systematic review

The question whether to use 2D or 3D for data visualization is generally difficult to decide. Two-dimensional and three-dimensional visualization techniques exhibit different advantages and disadvantages related to various perceptual and technical aspects such as occlusion, clutter, distortion, or scalability. To facilitate problem understanding and comparison of existing visualization techniques with regard to these aspects, this report introduces a systematization based on presentation characteristics. It enables a categorization with respect to combinations of static 2D and 3D presentations of attributes and their spatial reference. Further, it complements existing systematizations of data in an effort to formalize a common terminology and theoretical framework for this problem domain. We demonstrate our approach by reviewing different visualization techniques of spatial data according to the presented systematization.

Interactive Rendering Techniques for Highlighting in 3D Geovirtual Environments

3D geovirtual environments (GeoVE), such as virtual 3D city and landscape models become an important tool for the visualization of geospatial information. Highlighting is an important component within a visualization framework and is essential for the user interaction within many applications. It enables the user to easily perceive active or selected objects in the context of the current interaction task. With respect to 3D GeoVE, it has a number of applications, such as the visualization of user selections, data base queries, as well as navigation aid by highlighting way points, routes, or to guide the user attention. The geometrical complexity of 3D GeoVE often requires specialized rendering techniques for the real-time image synthesis. This paper presents a framework that unifies various highlighting techniques and is especially suitable for the interactive rendering 3D GeoVE of high geometrical complexity.

Real-time rendering of water surfaces with cartography-oriented design

More than 70% of the Earths surface is covered by oceans, seas, and lakes, making water surfaces one of the primary elements in geospatial visualization. Traditional approaches in computer graphics simulate and animate water surfaces in the most realistic ways. However, to improve orientation, navigation, and analysis tasks within 3D virtual environments, these surfaces need to be carefully designed to enhance shape perception and land-water distinction. We present an interactive system that renders water surfaces with cartography-oriented design using the conventions of mapmakers. Our approach is based on the observation that hand-drawn maps utilize and align texture features to shorelines with non-linear distance to improve figure-ground perception and express motion. To obtain local orientation and principal curvature directions, first, our system computes distance and feature-aligned distance maps. Given these maps, waterlining, water stippling, contour-hatching, and labeling are applied in real-time with spatial and temporal coherence. The presented methods can be useful for map exploration, landscaping, urban planning, and disaster management, which is demonstrated by various real-world virtual 3D city and landscape models.

Animated visualization of spatial---temporal trajectory data for air-traffic analysis

With increasing numbers of flights worldwide and a continuing rise in airport traffic, air-traffic management is faced with a number of challenges. These include monitoring, reporting, planning, and problem analysis of past and current air traffic, e.g., to identify hotspots, minimize delays, or to optimize sector assignments to air-traffic controllers. To cope with these challenges, cyber worlds can be used for interactive visual analysis and analytical reasoning based on aircraft trajectory data. However, with growing data size and complexity, visualization requires high computational efficiency to process that data within real-time constraints. This paper presents a technique for real-time animated visualization of massive trajectory data. It enables (1) interactive spatio-temporal filtering, (2) generic mapping of trajectory attributes to geometric representations and appearance, and (3) real-time rendering within 3D virtual environments such as virtual 3D airport or 3D city models. Different visualization metaphors can be efficiently built upon this technique such as temporal focus+context, density maps, or overview+detail methods. As a general-purpose visualization technique, it can be applied to general 3D and 3+1D trajectory data, e.g., traffic movement data, geo-referenced networks, or spatio-temporal data, and it supports related visual analytics and data mining tasks within cyber worlds.