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Helwig Hauser

University of Bergen, Department of Informatics, Faculty Member

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Visualization Research Group, http://www.ii.UiB.no/vis/
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Vrije Universiteit Brussel

School of the Art Institute of Chicago

Julita Vassileva

University of Saskatchewan

Duke University

Kwantlen Polytechnic University

Kansas State University

University of Haifa

Delft University of Technology

Graduate Center of the City University of New York

José d'Encarnação

Universidade de Coimbra

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Papers by Helwig Hauser

A survey of urban reconstruction

abstract={This paper provides a comprehensive overview of urban reconstruction. While there exist... more abstract={This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under very active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision, and photogrammetry and remote sensing.

State-of-the-art report 2002 in flow visualization

Abstract Flow visualization has been a very attractive field within visualization research for a ... more

Studying basin bifurcations in nonlinear triopoly games by using 3D visualization

Abstract We consider three-dimensional discrete dynamical system, obtained by the iteration of a ... more Abstract We consider three-dimensional discrete dynamical system, obtained by the iteration of a noninvertible map of M3, which simulates the time evolution of an oligopoly game with three competing firms. The model is characterized by the presence of several coexisting stable equilibria, each with its own basin of attraction. In this paper we face the question of the delimitation of the basins and the detection of the global bifurcations that cause the creation of non-connected basins.

ComVis: A coordinated multiple views system for prototyping new visualization technology

Abstract There is a large number of interactive visualization tools, however no universal tool ex... more Abstract There is a large number of interactive visualization tools, however no universal tool exists that covers all relevant aspects for all possible application domains. We have developed a tool, ComVis, which was intended to be used as are search prototype for new visualization techniques. We have identified some interesting aspects from developers' and users' points of view during tool development. In this paper we describe lessons learned during the process, and share our findings with visualization research community.

Texture advection on stream surfaces: A novel hybrid visualization applied to CFD simulation results

Abstract Stream surfaces are a classic flow visualization technique used to portray the character... more Abstract Stream surfaces are a classic flow visualization technique used to portray the characteristics of vector fields, and texture advection research has made rapid advances in recent years. We present a novel hybrid visualization of texture advection on stream surfaces. This approach conveys properties of the vector field that stream surfaces alone cannot.

Interactive visual analysis of perfusion data

Abstract Perfusion data are dynamic medical image data which characterize the regional blood flow... more Abstract Perfusion data are dynamic medical image data which characterize the regional blood flow in human tissue. These data bear a great potential in medical diagnosis, since diseases can be better distinguished and detected at an earlier stage compared to static image data. The wide-spread use of perfusion data is hampered by the lack of efficient evaluation methods. For each voxel, a time-intensity curve characterizes the enhancement of a contrast agent.

Toward a Lagrangian vector field topology

Abstract In this paper we present an extended critical point concept which allows us to apply vec... more Abstract In this paper we present an extended critical point concept which allows us to apply vector field topology in the case of unsteady flow. We propose a measure for unsteadiness which describes the rate of change of the velocities in a fluid element over time. This measure allows us to select particles for which topological properties remain intact inside a finite spatio-temporal neighborhood. One benefit of this approach is that the classification of critical points based on the eigenvalues of the Jacobian remains meaningful.

The InverseWarp: Non-Invasive Integration of Shear-Warp Volume Rendering into Polygon Rendering Pipelines

Abstract In this paper, a simple and efficient solution for combining shear-warp volume rendering... more Abstract In this paper, a simple and efficient solution for combining shear-warp volume rendering and the hardware graphics pipeline is presented. The approach applies an inverse warp transformation to the Z-Buffer, containing the rendered geometry. This information is used for combining geometry and volume data during compositing.

Sonography of the small intestine

Abstract In the last two decades, there has been substantial development in the diagnostic possib... more Abstract In the last two decades, there has been substantial development in the diagnostic possibilities for examining the small intestine. Compared with computerized tomography, magnetic resonance imaging, capsule endoscopy and double-balloon endoscopy, ultrasonography has the advantage of being cheap, portable, flexible and user-and patient-friendly, while at the same time providing the clinician with image data of high temporal and spatial resolution.

Semi-Global Visual Analysis of Multivariate Flow Simulation Data

Abstract In our work, we describe the benefits which we have achieved in the visual analysis of l... more Abstract In our work, we describe the benefits which we have achieved in the visual analysis of large flow simulation data by employing an iteractive, coordinated setup of views for attribute visualization as well as for semi-global flow analysis based on integral lines. We are able to simultaneously analyze the multivariate data while at the same time learning more about the related flow behavior.

Illustrative flow visualization: State of the art, trends and challenges

Abstract Flow visualization is a well established branch of scientific visualization and it curre... more Abstract Flow visualization is a well established branch of scientific visualization and it currently represents an invaluable resource to many fields, like automotive design, meteorology and medical imaging. Thanks to the capabilities of modern hardware, flow datasets are increasing in size and complexity, and traditional flow visualization techniques need to be updated and improved in order to deal with the upcoming challenges.

Similarity brushing for exploring multidimensional relations

ABSTRACT Displaying multidimensional information has always been a challenge. Projecting multiple... more ABSTRACT Displaying multidimensional information has always been a challenge. Projecting multiple dimensions into a two dimensional display is one of the core tasks of information visualization. The human visual system is limited to a low number of dimensions and therefore the human-oriented projection does not easily combine the whole information contained in the original space.

Access to surface properties up to order two for visualization algorithms

Summary. Elaborated visualization techniques which are based on surfaces often are independent fr... more Summary. Elaborated visualization techniques which are based on surfaces often are independent from the origin of the surface data. Nevertheless, many of the previously presented visualization methods were developed for a specific type of surface, although principally applicable to generic surfaces. In this paper we discuss a model for a general access to surface properties up to order two, ie, surface-point locations, normals, and curvature properties,(almost) regardless of the origin of the surface.

Hardware-accelerated high-quality filtering on PC hardware

Abstract We describe a method for exploiting commodity 3D graphics hardware in order to achieve h... more Abstract We describe a method for exploiting commodity 3D graphics hardware in order to achieve hardwareaccelerated high-quality filtering with arbitrary filter kernels. Our approach is based on reordering the evaluation of the filter convolution sum to accommodate the way the hardware works. We exploit multiple rendering passes together with the capability of current graphics hardware to index into several textures at the same time (multi-texturing). The method we present is applicable in one, two, and three dimensions.

Semantic depth of field

Abstract Pointing the user to the parts of a visual display that are currently the most relevant ... more Abstract Pointing the user to the parts of a visual display that are currently the most relevant is an important task in information visualization. The same problem exists in photography, where a number of solutions have been known for a long time. One of these methods is depth of field (DOF), which depicts objects in or out of focus depending on their distance from the camera.

Interactive visualization of streaming data with Kernel Density Estimation

Abstract In this paper, we discuss the extension and integration of the statistical concept of Ke... more Abstract In this paper, we discuss the extension and integration of the statistical concept of Kernel Density Estimation (KDE) in a scatterplot-like visualization for dynamic data at interactive rates. We present a line kernel for representing streaming data, we discuss how the concept of KDE can be adapted to enable a continuous representation of the distribution of a dependent variable of a 2D domain.

A statistics-based dimension reduction of the space of path line attributes for interactive visual flow analysis

Abstract Recent work has shown the great potential of interactive flow analysis by the analysis o... more Abstract Recent work has shown the great potential of interactive flow analysis by the analysis of path lines. The choice of suitable attributes, describing the path lines, is, however, still an open question. This paper addresses this question performing a statistical analysis of the path line attribute space. In this way we are able to balance the usage of computing power and storage with the necessity to not loose relevant information.

Interactive feature specification for simulation data on time-varying grids

Abstract SimVis is an interactive research implementation of a visual analysis scheme which we de... more Abstract SimVis is an interactive research implementation of a visual analysis scheme which we developed for the feature-based assessment of flow simulation data. It is based on the concept of multiple, linked views of different kinds, including views from information visualization such as adapted scatterplots and histograms. In this paper we present an extension to our interactive visual analysis framework, which allows to handle data resulting from CFD simulations which are based on timevarying grids.

A Four‐level Focus+ Context Approach to Interactive Visual Analysis of Temporal Features in Large Scientific Data

Abstract In this paper we present a new approach to the interactive visual analysis of time-depen... more Abstract In this paper we present a new approach to the interactive visual analysis of time-dependent scientific data–both from measurements as well as from computational simulation–by visualizing a scalar function over time for each of tenthousands or even millions of sample points. In order to cope with overdrawing and cluttering, we introduce a new four-level method of focus+ context visualization.

Mastering windows: Improving reconstruction

Abstract Ideal reconstruction filters, for function or arbitrary derivative reconstruction, have ... more Abstract Ideal reconstruction filters, for function or arbitrary derivative reconstruction, have to be bounded in order to be practicable since they are infinite in their spatial extent. This can be accomplished by multiplying them with windowing functions. In this paper we discuss and assess the quality of commonly used windows and show that most of them are unsatisfactory in terms of numerical accuracy. ftheussl, helwig, meisterg@ cg. tuwien. ac. at

A survey of urban reconstruction

abstract={This paper provides a comprehensive overview of urban reconstruction. While there exist... more abstract={This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under very active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision, and photogrammetry and remote sensing.

State-of-the-art report 2002 in flow visualization

Abstract Flow visualization has been a very attractive field within visualization research for a ... more

Studying basin bifurcations in nonlinear triopoly games by using 3D visualization

Abstract We consider three-dimensional discrete dynamical system, obtained by the iteration of a ... more Abstract We consider three-dimensional discrete dynamical system, obtained by the iteration of a noninvertible map of M3, which simulates the time evolution of an oligopoly game with three competing firms. The model is characterized by the presence of several coexisting stable equilibria, each with its own basin of attraction. In this paper we face the question of the delimitation of the basins and the detection of the global bifurcations that cause the creation of non-connected basins.

ComVis: A coordinated multiple views system for prototyping new visualization technology

Abstract There is a large number of interactive visualization tools, however no universal tool ex... more Abstract There is a large number of interactive visualization tools, however no universal tool exists that covers all relevant aspects for all possible application domains. We have developed a tool, ComVis, which was intended to be used as are search prototype for new visualization techniques. We have identified some interesting aspects from developers' and users' points of view during tool development. In this paper we describe lessons learned during the process, and share our findings with visualization research community.

Texture advection on stream surfaces: A novel hybrid visualization applied to CFD simulation results

Abstract Stream surfaces are a classic flow visualization technique used to portray the character... more Abstract Stream surfaces are a classic flow visualization technique used to portray the characteristics of vector fields, and texture advection research has made rapid advances in recent years. We present a novel hybrid visualization of texture advection on stream surfaces. This approach conveys properties of the vector field that stream surfaces alone cannot.

Interactive visual analysis of perfusion data

Abstract Perfusion data are dynamic medical image data which characterize the regional blood flow... more Abstract Perfusion data are dynamic medical image data which characterize the regional blood flow in human tissue. These data bear a great potential in medical diagnosis, since diseases can be better distinguished and detected at an earlier stage compared to static image data. The wide-spread use of perfusion data is hampered by the lack of efficient evaluation methods. For each voxel, a time-intensity curve characterizes the enhancement of a contrast agent.

Toward a Lagrangian vector field topology

Abstract In this paper we present an extended critical point concept which allows us to apply vec... more Abstract In this paper we present an extended critical point concept which allows us to apply vector field topology in the case of unsteady flow. We propose a measure for unsteadiness which describes the rate of change of the velocities in a fluid element over time. This measure allows us to select particles for which topological properties remain intact inside a finite spatio-temporal neighborhood. One benefit of this approach is that the classification of critical points based on the eigenvalues of the Jacobian remains meaningful.

The InverseWarp: Non-Invasive Integration of Shear-Warp Volume Rendering into Polygon Rendering Pipelines

Abstract In this paper, a simple and efficient solution for combining shear-warp volume rendering... more Abstract In this paper, a simple and efficient solution for combining shear-warp volume rendering and the hardware graphics pipeline is presented. The approach applies an inverse warp transformation to the Z-Buffer, containing the rendered geometry. This information is used for combining geometry and volume data during compositing.

Sonography of the small intestine

Abstract In the last two decades, there has been substantial development in the diagnostic possib... more Abstract In the last two decades, there has been substantial development in the diagnostic possibilities for examining the small intestine. Compared with computerized tomography, magnetic resonance imaging, capsule endoscopy and double-balloon endoscopy, ultrasonography has the advantage of being cheap, portable, flexible and user-and patient-friendly, while at the same time providing the clinician with image data of high temporal and spatial resolution.

Semi-Global Visual Analysis of Multivariate Flow Simulation Data

Abstract In our work, we describe the benefits which we have achieved in the visual analysis of l... more Abstract In our work, we describe the benefits which we have achieved in the visual analysis of large flow simulation data by employing an iteractive, coordinated setup of views for attribute visualization as well as for semi-global flow analysis based on integral lines. We are able to simultaneously analyze the multivariate data while at the same time learning more about the related flow behavior.

Illustrative flow visualization: State of the art, trends and challenges

Abstract Flow visualization is a well established branch of scientific visualization and it curre... more Abstract Flow visualization is a well established branch of scientific visualization and it currently represents an invaluable resource to many fields, like automotive design, meteorology and medical imaging. Thanks to the capabilities of modern hardware, flow datasets are increasing in size and complexity, and traditional flow visualization techniques need to be updated and improved in order to deal with the upcoming challenges.

Similarity brushing for exploring multidimensional relations

ABSTRACT Displaying multidimensional information has always been a challenge. Projecting multiple... more ABSTRACT Displaying multidimensional information has always been a challenge. Projecting multiple dimensions into a two dimensional display is one of the core tasks of information visualization. The human visual system is limited to a low number of dimensions and therefore the human-oriented projection does not easily combine the whole information contained in the original space.

Access to surface properties up to order two for visualization algorithms

Summary. Elaborated visualization techniques which are based on surfaces often are independent fr... more Summary. Elaborated visualization techniques which are based on surfaces often are independent from the origin of the surface data. Nevertheless, many of the previously presented visualization methods were developed for a specific type of surface, although principally applicable to generic surfaces. In this paper we discuss a model for a general access to surface properties up to order two, ie, surface-point locations, normals, and curvature properties,(almost) regardless of the origin of the surface.

Hardware-accelerated high-quality filtering on PC hardware

Abstract We describe a method for exploiting commodity 3D graphics hardware in order to achieve h... more Abstract We describe a method for exploiting commodity 3D graphics hardware in order to achieve hardwareaccelerated high-quality filtering with arbitrary filter kernels. Our approach is based on reordering the evaluation of the filter convolution sum to accommodate the way the hardware works. We exploit multiple rendering passes together with the capability of current graphics hardware to index into several textures at the same time (multi-texturing). The method we present is applicable in one, two, and three dimensions.

Semantic depth of field

Abstract Pointing the user to the parts of a visual display that are currently the most relevant ... more Abstract Pointing the user to the parts of a visual display that are currently the most relevant is an important task in information visualization. The same problem exists in photography, where a number of solutions have been known for a long time. One of these methods is depth of field (DOF), which depicts objects in or out of focus depending on their distance from the camera.

Interactive visualization of streaming data with Kernel Density Estimation

Abstract In this paper, we discuss the extension and integration of the statistical concept of Ke... more Abstract In this paper, we discuss the extension and integration of the statistical concept of Kernel Density Estimation (KDE) in a scatterplot-like visualization for dynamic data at interactive rates. We present a line kernel for representing streaming data, we discuss how the concept of KDE can be adapted to enable a continuous representation of the distribution of a dependent variable of a 2D domain.

A statistics-based dimension reduction of the space of path line attributes for interactive visual flow analysis

Abstract Recent work has shown the great potential of interactive flow analysis by the analysis o... more Abstract Recent work has shown the great potential of interactive flow analysis by the analysis of path lines. The choice of suitable attributes, describing the path lines, is, however, still an open question. This paper addresses this question performing a statistical analysis of the path line attribute space. In this way we are able to balance the usage of computing power and storage with the necessity to not loose relevant information.

Interactive feature specification for simulation data on time-varying grids

Abstract SimVis is an interactive research implementation of a visual analysis scheme which we de... more Abstract SimVis is an interactive research implementation of a visual analysis scheme which we developed for the feature-based assessment of flow simulation data. It is based on the concept of multiple, linked views of different kinds, including views from information visualization such as adapted scatterplots and histograms. In this paper we present an extension to our interactive visual analysis framework, which allows to handle data resulting from CFD simulations which are based on timevarying grids.

A Four‐level Focus+ Context Approach to Interactive Visual Analysis of Temporal Features in Large Scientific Data

Abstract In this paper we present a new approach to the interactive visual analysis of time-depen... more Abstract In this paper we present a new approach to the interactive visual analysis of time-dependent scientific data–both from measurements as well as from computational simulation–by visualizing a scalar function over time for each of tenthousands or even millions of sample points. In order to cope with overdrawing and cluttering, we introduce a new four-level method of focus+ context visualization.

Mastering windows: Improving reconstruction

Abstract Ideal reconstruction filters, for function or arbitrary derivative reconstruction, have ... more Abstract Ideal reconstruction filters, for function or arbitrary derivative reconstruction, have to be bounded in order to be practicable since they are infinite in their spatial extent. This can be accomplished by multiplying them with windowing functions. In this paper we discuss and assess the quality of commonly used windows and show that most of them are unsatisfactory in terms of numerical accuracy. ftheussl, helwig, meisterg@ cg. tuwien. ac. at