Gesture typing is a stroke-based text input method for mobile devices. Instead of tapping, the user enters a word by gesturing through all its letters on a virtual keyboard with a single continuous stroke. Even though gesture typing is a widely available text entry method for mobile devices, very little is known about the underlying movement dynamics. The present work fills this gap in the literature by establishing a physiological movement model for gesture typing. We show that many features of word gestures can be described by the mathematical framework of a handwriting model. We extend the model to respect the particularities of gesture typing and show that the exact trajectories as well as the velocity profiles of most word gestures can be represented with a high accuracy. We present an algorithm to extract the model parameters from real gestures. Finally, we introduce a framework capable of synthesizing the trajectories of word gestures that share many features with human-generated gestures. We use these synthetic gestures to automatically evaluate gesture recognition algorithms with thousands of gestures.

It is well known that distance estimation in immersive virtual reality environments suffers from compression when viewed from an egocentric perspective with a head mounted display. While previous research indicates that providing the user with a virtual avatar with high geometric and motion fidelity may alleviate this problem, little work has been done to investigate which properties of the avatar's representation influence the distance estimation and how. In this poster we report the results of an evaluation of the user's distance perception with different avatar representations. Our results indicate that anthropometric fidelity of the avatar has stronger effect on the distance perception than its visual fidelity.

Gesture typing is a popular stroke-based text input method for mobile devices. Instead of tapping, the user enters a word with a single continuous stroke by gesturing through all the letters. In this paper, we introduce a quantitative motor control model to predict the human performance of gesture typing in terms of production times. Based on a model of cursive handwriting, it can be applied to predict the influence of the keyboard layout on gesture typing performance. In contrast to previous approaches, the "chunking" of multiple movements into a single action, which is observed for expert users, is a natural characteristic of the proposed model that avoids over-estimation of the production times. Data collected from gesture keyboard users is evaluated to assess the performance of the model in comparison to previous models.

Gesture typing is a popular text input method used on smartphones. Gesture keyboards are based on word gestures that subsequently trace all letters of a word on a virtual keyboard. Instead of tapping a word key by key, the user enters a word gesture with a single continuous stroke. In this paper, we introduce an implicit user verification approach for short text messages that are entered with a gesture keyboard. We utilize the way people interact with gesture keyboards to extract behavioral biometric features. We propose a proof-of-concept classification framework that learns the gesture typing behavior of a person and is able to decide whether a gestured message was written by the legitimate user or an imposter. Data collected from gesture keyboard users in a user study is used to assess the performance of the classification framework, demonstrating that the technique has considerable promise.

While touch technology has proven its usability for 2D interaction and has already become a standard input modality for many devices, the challenges to exploit its applicability with stereoscopically rendered content have barely been studied. In this paper we exploit the properties of the visual perception to allow users to touch stereoscopically displayed objects when the input is constrained to a 2D surface. Therefore, we have extended and generalized recent evaluations on the user's ability to discriminate small induced object shifts while reaching out to touch a virtual object, and we propose a practical interaction technique, the attracting shift technique, suitable for numerous application scenarios where shallow depth interaction is sufficient. In addition, our results indicate that slight object shifts during touch interaction make the virtual scene appear perceptually more stable compared to a static scene. As a consequence, applications have to manipulate the virtual objects to make them appear static for the user.

Behavioral biometrics derived from the fingertip movement on the touchscreen of a mobile device is a promising new authentication technique. A user is verified by the inherent, unique characteristics of the fingertip movement. In this paper, we present a novel verification system that combines these biometrics with a challenge and response type of authentication. The key feature of our technique is that it does not rely on any secret graphical password or gesture. Instead, the user is asked to perform a different, simple challenge on the touchscreen at each login attempt. The novel technique is therefore robust against replay and “smudge” attacks. Additionally, it does not require the user to remember any kind of secret password. We utilize pattern recognition techniques to extract unique behavioral characteristics of an individual. In a user study, we achieved an accuracy of 90% using our system with a single finger gesture, that can be performed in less than three seconds.

In this paper we present DigiTap---a wrist-worn device specially designed for symbolic input in virtual and augmented reality (VR/AR) environments. DigiTap is able to robustly sense thumb-to-finger taps on the four fingertips and the eight minor knuckles. These taps are detected by an accelerometer, which triggers capturing of an image sequence with a small wrist-mounted camera. The tap position is then extracted with low computational effort from the images by an image processing pipeline. Thus, the device is very energy efficient and may potentially be integrated in a smartwatch-like device, allowing an unobtrusive, always available, eyes-free input. To demonstrate the feasibility of our approach an initial user study with our prototype device was conducted. In this study the suitability of the twelve tapping locations was evaluated, and the most prominent sources of error were identified. Our prototype system was able to correctly classify 92% of the input locations.

As applications originating on desktop computers find their way onto multi-touch enabled mobile devices many interaction tasks that were designed for computer mice spread to new touch-based environments. One example is region selection, for instance in image editing applications. Several studies already investigated multi-touch object selections however, region selections have not been closely examined.

Abstract Cardiovascular diseases are the main cause of death in the western world. Medical research on atherosclerosis is therefore of great interest and a very active research topic. We present a visualization system that supports scientists in exploring plaque development and evaluating the applicability of PET tracers for early diagnosis of cardiovascular diseases. In our application case a cone shaped cuff has been implanted around the carotid artery of ApoE knockout mice, fed with a high cholesterol western type diet. As a result, vascular lesions develop upstream and downstream from the cuff. Tracer uptake induced by these lesions needs to be analyzed in order to evaluate the effectiveness of different PET tracers. We discuss the approach previously utilized to perform this kind of analysis, the problems arising from in vivo image acquisition (in contrast to ex vivo) and the design process of our application. In close cooperation with domain experts we have developed new visualization techniques that display PET activity in the vessel wall and surrounding tissue in a single image. We use the vessel wall detected in the CT image to perform a normalized circular projection which allows the user to judge PET signal distribution in relation to the deformed vessel. Based on this projection a quantitative analysis of a defined region adjacent to the vessel wall can be performed and compared to the artery without the cuff.

Traditionally, interaction techniques for virtual reality applications are implemented in a proprietary way on specific target platforms, e. g., requiring specific hardware, physics or rendering libraries, which hinders reusability and portability. Even though abstraction layers for hardware devices are provided by numerous virtual reality libraries, they are usually tightly bound to a particular rendering environment and hardware configuration. In this paper we introduce VINS (Virtual Interactive Namespace) a seamless distributed memory space, which provides a hierarchical structure to support reusable design of interactive techniques. With VINS an interaction metaphor, whether it is implemented as function or class in the main application thread, uses its own thread or runs as its own process on another computer, can be transferred from one application to another without modifications. We describe the underlying concepts and present examples on how to integrate VINS with different frameworks or already implemented interactive techniques.

In this paper, we describe a novel approach for applying texture mapping to volumetric data sets. In contrast to previous approaches, the presented technique enables a unified integration of 2D and 3D textures and thus allows to emphasize material boundaries as well as volumetric regions within a volumetric data set at the same time. One key contribution of this paper is a parametrization technique for volumetric data sets, which takes into account material boundaries and volumetric regions. Using this technique, the resulting parametrizations of volumetric data sets enable texturing effects which create a higher degree of realism in volume rendered images. We evaluate the quality of the parametrization and demonstrate the usefulness of the proposed concepts by combining volumetric texturing with volumetric lighting models to generate photorealistic volume renderings. Furthermore, we show the applicability in the area of illustrative visualization.

The trackball metaphor is exploited in many applications where volumetric data needs to be explored. Although it provides an intuitive way to inspect the overall structure of objects of interest, an in-detail inspection can be tedious - or when cavities occur even impossible. Therefore we propose a context-aware navigation technique for the exploration of volumetric data. While navigation techniques for polygonal data require information about the rendered geometry, this strategy is not sufficient in the area of volume rendering. Since rendering parameters, e.g., the transfer function, have a strong influence on the visualized structures, they also affect the features to be explored. To compensate for this effect we propose a novel image-based navigation approach for volumetric data. While being intuitive to use, the proposed technique allows the user to perform complex navigation tasks, in particular to get an overview as well as to perform an in-detail inspection without any navigation mode switches. The technique can be easily integrated into raycasting based volume renderers, needs no extra data structures and is independent of the data set as well as the rendering parameters. We will discuss the underlying concepts, explain how to enable the navigation at interactive frame rates using OpenCL, and evaluate its usability as well as its performance.

Recent developments in the area of touch and display technologies have suggested to combine multi-touch systems and stereoscopic visualization. Stereoscopic perception requires each eye to see a slightly different perspective of the same scene, which results in two distinct projections on the display. Thus, if the user wants to select a 3D stereoscopic object in such a setup, the question arises where she would touch the 2D surface to indicate the selection. A user may apply different strategies, for instance touching the midpoint between the two projections, or touching one of them.

In visual perception, change blindness describes the phenomenon that persons viewing a visual scene may apparently fail to detect significant changes in that scene. These phenomena have been observed in both computer-generated imagery and real-world scenes. Several studies have demonstrated that change blindness effects occur primarily during visual disruptions such as blinks or saccadic eye movements. However, until now the influence of stereoscopic vision on change blindness has not been studied thoroughly in the context of visual perception research. In this paper, we introduce change blindness techniques for stereoscopic virtual reality (VR) systems, providing the ability to substantially modify a virtual scene in a manner that is difficult for observers to perceive. We evaluate techniques for semiimmersive VR systems, i.e., a passive and active stereoscopic projection system as well as an immersive VR system, i.e., a head-mounted display, and compare the results to those of monoscopic viewing conditions. For stereoscopic viewing conditions, we found that change blindness phenomena occur with the same magnitude as in monoscopic viewing conditions. Furthermore, we have evaluated the potential of the presented techniques for allowing abrupt, and yet significant, changes of a stereoscopically displayed virtual reality environment.

The display units integrated in today's head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display field of view (DFOV). A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. It has been shown that this distortion has the potential to affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks. In this paper, we analyze the user's perception of a VE displayed in a HMD, which is rendered with different GFOVs. We introduce a psychophysical calibration method to determine the HMD's actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects--even if these perspectives deviate from the perspectives that are inherently defined by the DFOV. In the first experiment, subjects had to adjust the GFOV for a rendered virtual laboratory such that their perception of the virtual replica matched the perception of the real laboratory, which they saw before the virtual one. In the second experiment, we displayed the same virtual laboratory, but restricted the viewing condition in the real world to simulate the limited viewing condition in a HMD environment. We found that subjects evaluate a GFOV as natural when it is larger than the actual DFOV of the HMD--in some cases up to 50 percent--even when subjects viewed the real space with a limited field of view.

We present a novel classification technique for volume visualization that takes the shape of volumetric features into account. The presented technique enables the user to distinguish features based on their 3D shape and to assign individual optical properties to these. Based on a rough pre-segmentation that can be done by windowing, we exploit the curve-skeleton of each volumetric structure in order to derive a shape descriptor similar to those used in current shape recognition algorithms. The shape descriptor distinguishes three main shape classes: longitudinal, surface-like, and blobby shapes. In contrast to previous approaches, the classification is not performed on a per-voxel level but assigns a uniform shape descriptor to each feature and therefore allows a more intuitive user interface for the assignment of optical properties. By using the proposed technique, it becomes for instance possible to distinguish blobby heart structures filled with contrast agents from potentially occluding vessels and rib bones. After introducing the basic concepts, we show how the presented technique performs on real world data, and we discuss current limitations.

Miniaturized unmanned flying robots, also referred to as MUAVs (Micro Unmanned Aerial Vehicles) open up completely new fields of innovative applications in the areas of civil security, cellular networks, surveying, entertainment and media. The AVIGLE project is based on the vision of a novel, widely applicable avionic service platform which supports multiple high-tech services by using open interfaces. Recent developments in the area of lithium polymer batteries and carbon fiber-reinforced plastic materials let MUAVs become an aerial platform, that can be equipped with a variety of sensors such as image or time of flight (ToF) cameras. Furthermore, it is also possible to mount communication technologies on the platform in order to let the MUAVs work as communication hot spots or relais at places where no cellular networks are available. In this paper we present a system of systems concept of an Unmanned Aerial System working as a service platform for different Concepts of Operations (ConOps).

In visual perception, change blindness describes the phenomenon that persons viewing a visual scene may apparently fail to detect significant changes in that scene. These phenomena have been observed in both computer generated imagery and real-world scenes. Several studies have demonstrated that change blindness effects occur primarily during visual disruptions such as blinks or saccadic eye movements. However, until now the influence of stereoscopic vision on change blindness has not been studied thoroughly in the context of visual perception research. In this paper we introduce change blindness techniques for stereoscopic projection systems, providing the ability to substantially modify a virtual scene in a manner that is difficult for observers to perceive. We evaluate techniques for passive and active stereoscopic viewing and compare the results to those of monoscopic viewing conditions. For stereoscopic viewing conditions, we found that change blindness phenomena occur with the same magnitude as in monoscopic viewing conditions. Furthermore, we have evaluated the potential of the presented techniques for allowing abrupt, and yet significant, changes of a stereoscopically displayed virtual reality environment.

Physical characteristics and constraints of today's head-mounted displays (HMDs) often impair interaction in immersive virtual environments (VEs). For instance, due to the limited field of view (FOV) subtended by the display units in front of the user's eyes more effort is required to explore a VE by head rotations than for exploration in the real world.

Although direct volume rendering is established as a powerful tool for the visualization of volumetric data, efficient and reliable feature detection is still an open topic. Usually, a tradeoff between fast but imprecise classification schemes and accurate but time-consuming segmentation techniques has to be made. Furthermore, the issue of uncertainty introduced with the feature detection process is completely neglected by the majority of existing approaches.In this paper we propose a guided probabilistic volume segmentation approach that focuses on the minimization of uncertainty. In an iterative process, our system continuously assesses uncertainty of a random walker-based segmentation in order to detect regions with high ambiguity, to which the user's attention is directed to support the correction of potential misclassifications. This reduces the risk of critical segmentation errors and ensures that information about the segmentation's reliability is conveyed to the user in a dependable way. In order to improve the efficiency of the segmentation process, our technique does not only take into account the volume data to be segmented, but also enables the user to incorporate classification information. An interactive workflow has been achieved by implementing the presented system on the GPU using the OpenCL API. Our results obtained for several medical data sets of different modalities, including brain MRI and abdominal CT, demonstrate the reliability and efficiency of our approach.

In order to increase a user's sense of presence in an artificial environment some researchers propose a gradual transition from reality to the virtual world instead of immersing users into the virtual world directly. One approach is to start the VR experience in a virtual replica of the physical space to accustom users to the characteristics of VR, e.g., latency, reduced field of view or tracking errors, in a known environment. Although this procedure is already applied in VR demonstrations, until now it has not been verified whether the usage of such a transitional environment - as transition between real and virtual environment - increases someone's sense of presence. We have observed subjective, physiological and behavioral reactions of subjects during a fully-immersive flight phobia experiment under two different conditions: the virtual flight environment was displayed immediately, or subjects visited a transitional environment before entering the virtual flight environment. We have quantified to what extent a gradual transition to the VE via a transitional environment increases the level of presence. We have found that subjective responses show significantly higher scores for the user's sense of presence, and that subjects' behavioral reactions change when a transitional environment is shown first. Considering physiological reactions, no significant difference could be found.

The display units integrated in todays head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display's field of view. A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. Discrepancies between the geometric and physical FOV causes the imagery to be minified or magnified. This distortion has the potential to negatively or positively affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks.

In this paper, we present a visualization system for the visual analysis of PET/CT scans of aortic arches of mice. The system has been designed in close collaboration between researchers from the areas of visualization and molecular imaging with the objective to get deeper insights into the structural and molecular processes which take place during plaque development. Understanding the development of plaques might lead to a better and earlier diagnosis of cardiovascular diseases, which are still the main cause of death in the western world. After motivating our approach, we will briefly describe the multimodal data acquisition process before explaining the visualization techniques used. The main goal is to develop a system which supports visual comparison of the data of different species. Therefore, we have chosen a linked multi-view approach, which amongst others integrates a specialized straightened multipath curved planar reformation and a multimodal vessel flattening technique. We have applied the visualization concepts to multiple data sets, and we will present the results of this investigation.

Traveling through immersive virtual environments (IVEs) by means of real walking is an important activity to increase naturalness of VR-based interaction. However, the size of the virtual world often exceeds the size of the tracked space so that a straightforward implementation of omni-directional and unlimited walking is not possible. Redirected walking is one concept to solve this problem of walking in IVEs by inconspicuously guiding the user on a physical path that may differ from the path the user visually perceives. When the user approaches a virtual object she can be redirected to a real proxy object that is registered to the virtual counterpart and provides passive haptic feedback. In such passive haptic environments, any number of virtual objects can be mapped to proxy objects having similar haptic properties, e.g., size, shape and texture. The user can sense a virtual object by touching its real world counterpart. Redirecting a user to a registered proxy object makes it necessary to predict the user's intended position in the IVE. Based on this target position we determine a path through the physical space such that the user is guided to the registered proxy object. We present a taxonomy of possible redirection techniques that enable user guidance such that inconsistencies between visual and proprioceptive stimuli are imperceptible. We describe how a user's target in the virtual world can be predicted reliably and how a corresponding real-world path to the registered proxy object can be derived.

In this paper we introduce a virtual locomotion system that allows navigation within any large-scale virtual environment (VE) by real walking. In contrast to the work of Razzaque et al. (2001) we have developed generic redirected walking concepts by combining motion compression, i. e., scaling the real distance users walk, rotation gains, which make the real turns smaller or larger, and curvature gains, which bend the user's walking direction such that s/he walks on a curve. Furthermore, we introduce the new concept of dynamic passive haptics which extends passive haptics (Insko et al., 2001; Kohli et al., 2005) in such a way that any number of virtual objects can be sensed by means of real proxy objects having similar haptic capabilities, i. e., size, shape and surface structure. We have evaluated these concepts and explain technical details regarding their integration into legacy 3D graphics applications.

Abstract We propose a method for rendering volumetric data sets at interactive frame rates while supporting dynamic ambient occlusion as well as an approximation to color bleeding. In contrast to ambient occlusion approaches for polygonal data, techniques for volumetric data sets have to face additional challenges, since by changing rendering parameters, such as the transfer function or the thresholding, the structure of the data set and thus the light interactions may vary drastically. Therefore, during a preprocessing step which is independent of the rendering parameters we capture light interactions for all combinations of structures extractable from a volumetric data set. In order to compute the light interactions between the different structures, we combine this preprocessed information during rendering based on the rendering parameters defined interactively by the user. Thus our method supports interactive exploration of a volumetric data set but still gives the user control over the most important rendering parameters. For instance, if the user alters the transfer function to extract different structures from a volumetric data set the light interactions between the extracted structures are captured in the rendering while still allowing interactive frame rates. Compared to known local illumination models for volume rendering our method does not introduce any substantial rendering overhead and can be integrated easily into existing volume rendering applications. In this paper we will explain our approach, discuss the implications for interactive volume rendering and present the achieved results.

Myocardial perfusion imaging with single photon emission computed tomography (SPECT) is an established method for the detection and evaluation of coronary artery disease (CAD). State-of-the-art SPECT scanners yield a large number of regional parameters of the left-ventricular myocardium (e.g., blood supply at rest and during stress, wall thickness, and wall thickening during heart contraction) that all need to be assessed by the physician. Today, the individual parameters of this multivariate data set are displayed as stacks of 2D slices, bull's eye plots, or, more recently, surfaces in 3D, which depict the left-ventricular wall. In all these visualizations, the data sets are displayed side-by-side rather than in an integrated manner, such that the multivariate data have to be examined sequentially and need to be fused mentally. This is time consuming and error-prone. In this paper we present an interactive 3D glyph visualization, which enables an effective integrated visualization of the multivariate data. Results from semiotic theory are used to optimize the mapping of different variables to glyph properties. This facilitates an improved perception of important information and thus an accelerated diagnosis. The 3D glyphs are linked to the established 2D views, which permit a more detailed inspection, and to relevant meta-information such as known stenoses of coronary vessels supplying the myocardial region. Our method has demonstrated its potential for clinical routine use in real application scenarios assessed by nuclear physicians.

In this paper we introduce new user interface concepts for fish tank virtual reality (VR) systems based on autostereoscopic (AS) display technologies. Such AS displays allow to view stereoscopic content without requiring special glasses. Unfortunately, until now simultaneous monoscopic and stereoscopic display was not possible. Hence prior work on fish tank VR systems focussed either on 2D or 3D interactions. In this paper we introduce so called interscopic interaction concepts providing an improved working experience, which enable great potentials in terms of the interaction between 2D elements, which may be displayed either in monoscopic or stereoscopic, e.g., GUI items, and the 3D virtual environment usually displayed stereoscopically. We present a framework which is based on a software layer between the operating system and its graphical user interface supporting the display of both mono- as well as stereoscopic content in arbitrary regions of an autostereoscopic display. The proposed concepts open up new vistas for the interaction in environments where essential parts of the GUI are displayed monoscopically and other parts are rendered stereoscopically. We address some essential issues of such fish tank VR systems and introduce intuitive interaction concepts which we have realized

Figure 1: Using hybrid travel approaches (left) in outdoor pedestrian mode using scaled user movements in a 3D building evaluation system, (middle) in indoor pedestrian mode displayed in Google Earth, and (right) in outdoor mode in Microsoft Virtual Earth. In this paper we present hybrid traveling concepts that enable users to navigate immersively through 3D geospatial environments displayed by arbitrary applications such as Google Earth or Microsoft Virtual Earth. We propose a framework which allows to integrate virtual reality (VR) based interaction devices and concepts into such applications that do not support VR technologies natively. In our proposed setup the content displayed by a geospatial application is visualized stereoscopically on a head-mounted display (HMD) for immersive exploration. The user’s body is tracked in order to support natural traveling through the VE via a walking metaphor. Since the VE usually exceeds the dimension of the area in which the user can be tracked, we propose different strategies to map the user’s movement into the virtual world intuitively. Moreover, commonly available devices and interaction techniques are presented for both-handed interaction to enrich the navigation process.

This article addresses the problem of managing Moving Objects Databases (MODs) which capture the inherent imprecision of the information about the moving object's location at a given time. We deal systematically with the issues of constructing and representing the trajectories of moving objects and querying the MOD. We propose to model an uncertain trajectory as a three-dimensional (3D) cylindrical body and we introduce a set of novel but natural spatio-temporal operators which capture the uncertainty and are used to express spatio-temporal range queries. We devise and analyze algorithms for processing the operators and demonstrate that the model incorporates the uncertainty in a manner which enables efficient querying, thus striking a balance between the modeling power and computational efficiency. We address some implementation aspects which we experienced in our DOMINO project, as a part of which the operators that we introduce have been implemented. We also report on some experimental observations of a practical relevance.

Describes the software architecture of a rendering system that follows a pragmatic approach to integrating and bundling the power of different low-level rendering systems within an object-oriented framework. The generic rendering system provides higher-level abstractions to existing rendering systems and serves as a framework for developing new rendering techniques. It wraps the functionality of several widely-used rendering systems, defines a unified object-oriented application programming interface and provides an extensible, customizable apparatus for evaluating and interpreting hierarchical scene information. As a fundamental property, individual features of a specific rendering system can be integrated into the generic rending system in a transparent way. The system is based on a state machine, called an "engine", which operates on "rendering components". Four major categories of rendering components constitute the generic rendering system: "shapes" represent geometries, "attributes" specify properties assigned to geometries and scenes, "handlers" encapsulate rendering algorithms, and "techniques" represent evaluation strategies for rendering components. As a proof of concept, we have implemented the described software architecture using the Virtual Rendering System, which currently wraps the functionality of the OpenGL, Radiance, POV Ray and RenderMan systems.

Three-dimensional maps are fundamental tools for presenting, exploring, and manipulating geo data. This paper describes multiresolution concepts for 3D maps and their texture-based design. In our approach, 3D maps are based on a hybrid, multiresolution terrain model composed of data sets having different topological structure, for example a coarse regular grid combined with by triangulated microstructure. Any number of texture layers can be associated with the terrain model. For each texture layer, the multiresolution structure builds a texture tree which is linked to geometry patches of the multiresolution terrain model. The terrain model together with multiple texture layers can be rendered in real-time, in particular if multitexturing is available. Texture layers can be combined by high-level operations such us blending and masking and can be rebuilt at run-time. This mechanism simplifies the implementation of visual exploration tools and of procedural, automated map designs. 3D maps facilitate the visual simulation of environmental issues in spatial support systems, virtual reality applications, real-time GIS, and interactive cartography.

Presents a new rendering technique for processing multiple multi-resolution textures of LOD (level-of-detail) terrain models and describes its application to interactive, animated terrain content design. The approach is based on a multi-resolution model for terrain texture which cooperates with a multi-resolution model for terrain geometry. For each texture layer, an image pyramid and a texture tree are constructed. Multiple texture layers can be associated with one terrain model and can be combined in different ways, e.g. by blending and masking. The rendering algorithm simultaneously traverses the multi-resolution geometry model and the multi-resolution texture model, and takes into account geometric and texture approximation errors. It uses multi-pass rendering and exploits multi-texturing to achieve real-time performance. Applications include interactive texture lenses, texture animation and topographic textures. These techniques offer an enormous potential for developing new visualization applications for presenting, exploring and manipulating spatio-temporal data.

The approximation tree is a hybrid, hierarchical data structure for real-time terrain visualization which represents both geometry data and texture data of a terrain in a hierarchical manner. This framework can integrate different multiresolution modeling techniques operating on different types of data sets such as TLNs, regular grids, and non-regular grids. An approximation tree recursively aggregates terrain patches which reference geometry data and texture data. The rendering algorithm selects patches based on a geometric approximation error and a texture approximation error. Terrain shading and thematic texturing, which can be generated in a preprocessing step, improve the visual quality of level of detail models and eliminate the defects resulting from a Gouraud shaded geometric model since they do not depend on the current (probably reduced) geometry. The approximation tree can be implemented efficiently using object-oriented design principles. A case study for cartographic landscape visualization illustrates the use of approximation trees.

If 3D applications become large, hierarchical networks of geometric objects lead to messy specifications. Furthermore, if time- and event-dependencies are merged with geometric modeling, complex animations and interactions cannot be modeled independently and hierarchically since their specifications are dispersed throughout the static scene description. The authors present an object-oriented architecture for interactive, animated 3D widgets which reduces the complexity of building 3D applications. 3D widgets encapsulate geometry and behavior into high-level building blocks based on two types of directed acyclic graphs, geometry graphs and behavior graphs. 3D widgets construct internal geometry graphs and behavior graphs, and perform operations on these graphs through high-level interfaces which hide details and raise the level of abstraction. 3D widgets define object ports which are used to link together different 3D widgets. A visual language for 3D widgets allows the developer the interactive construction of 3D applications.

Article Free Access Share on An interactive environment for visualizing and animating algorithms Authors: Júrgen Döllner FB 15, Institut für Informatik, Westfälische Wilhelms-Universität, Einsteinstr. 62, D - 48149 Münster, Germany FB 15, Institut für Informatik, Westfälische Wilhelms-Universität, Einsteinstr. 62, D - 48149 Münster, GermanyView Profile , Klaus Hinrichs FB 15, Institut für Informatik, Westfälische Wilhelms-Universität, Einsteinstr. 62, D - 48149 Münster, Germany FB 15, Institut für Informatik, Westfälische Wilhelms-Universität, Einsteinstr. 62, D - 48149 Münster, GermanyView Profile , Hermann Spiegel FB 15, Institut für Informatik, Westfälische Wilhelms-Universität, Einsteinstr. 62, D - 48149 Münster, Germany FB 15, Institut für Informatik, Westfälische Wilhelms-Universität, Einsteinstr. 62, D - 48149 Münster, GermanyView Profile Authors Info & Claims SCG '97: Proceedings of the thirteenth annual symposium on Computational geometryAugust 1997 Pages 409–411https://doi.org/10.1145/262839.263032Published:01 August 1997Publication History 0citation294DownloadsMetricsTotal Citations0Total Downloads294Last 12 Months4Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

We present an object-oriented 3D graphics and animation framework which provides a new methodology for the symmetric modelling of geometry and behaviour. The toolkit separates the specification of geometry and behaviour by two types of directed acyclic graphs, the geometry graph and the behaviour graph, which are linked together through constraint relations. All geometry objects and behaviour objects are represented as DAG nodes. The geometry graph provides a renderer-independent hierarchical description of 3D scenes and rendering processes. The behaviour graph specifies time- and event-dependent constraints applied to graphics objects. Behaviour graphs simplify the specification of complex animations and 3D interactions by providing nodes for the management of the time and event flow (e.g. durations, time layouts, time repeaters, actions). Nodes contain, manipulate and share instances of constrainable graphical abstract data types. Geometry nodes and behaviour nodes are used to configure high-level 3D widgets, i.e. high-level building blocks for constructing 3D applications. The fine-grained object structure of the system leads to an extensible reusable framework which can be implemented efficiently. © 1997 by John Wiley & Sons, Ltd.

We present an algorithm which computes the overlay Hb r+ rIg of two Simply connected planar subdivisions ~b and Hg; we assume that ~b (resp.~) and all its components are colored in blue (resp.green).The algorithm runs in O(n + k) time and space, where n denotes the total nuruber of edges of ~b and IIg and k the number of intersections between blue and green edges.

The BR/sup 2/-directory representation, a directory structure for grid files, and a join algorithm for the evaluation of general n-ary joins on grid files are presented. It is shown that the CPU cost of the join algorithm is successfully reduced by introducing an inner join. A comparison with the hash join algorithm and a join algorithm on k-d trees for equijoins is based on a cost model developed for query processing with grid files. The join algorithm outperforms the hash join, a specialized join method for equijoins, and the join algorithm on k-d trees for equijoins.>