Sebastian Thelen

Full-resolution interactive CPU volume rendering with coherent BVH traversal

We present an efficient method for volume rendering by raycasting on the CPU. We employ coherent packet traversal of an implicit bounding volume hierarchy, heuristically pruned using preintegrated transfer functions, to exploit empty or homogeneous space. We also detail SIMD optimizations for volumetric integration, trilinear interpolation, and gradient lighting. The resulting system performs well on low-end and laptop hardware, and can outperform out-of-core GPU methods by orders of magnitude when rendering large volumes without level-of-detail (LOD) on a workstation. We show that, while slower than GPU methods for low-resolution volumes, an optimized CPU renderer does not require LOD to achieve interactive performance on large data sets.

Advanced Visualization and Interaction Techniques for Large High-Resolution Displays

Large high-resolution displays combine the images of multiple smaller display devices to form one large display area. A total resolution that can easily comprise several hundred megapixels makes them suited for the visualization of data sets that could not be perceived entirely on desktop PCs or laptops due to their size. At the same time, user collaboration benefits from an extended screen area that facilitates interaction with screen contents as well as interaction among users. This paper discusses the challenges and opportunities of large high-resolution displays and examines ways to set up display clusters both in terms of hardware and underlying software technology. Furthermore, it investigates how to eectively harness the computational power and resources of rendering clusters to visualize giga-scale data sets. Last but not least, traditional interaction metaphors and their scalability to large displays as well as the eect of new techniques on the user experience are discussed.

Giga-scale multiresolution volume rendering on distributed display clusters

Visualizing the enormous level of detail comprised in many of todays data sets is a challenging task and demands special processing techniques as well as a presentation on appropriate display devices. Desktop computers and laptops are often not suited for this task because data sets are simply too large and the limited screen size of these devices prevents users from perceiving the entire data set and severely restricts collaboration. Large high-resolution displays that combine the images of multiple smaller devices to form one large display area have proven to be an adequate solution to the ever-growing quantity of available data. The displays offer enough screen real estate to visualize such data sets entirely and facilitate collaboration, since multiple users are able to perceive the information at the same time. For an interactive visualization, the CPUs on the cluster driving the GPUs can be used to split up the computation of a scene into different areas, where each area is computed by a different rendering node. In this paper we focus on volumetric data sets and introduce a dynamic subdivision scheme incorporating multi-resolution wavelet representation to visualize data sets with several gigabytes of voxel data interactively on distributed rendering clusters. The approach makes efficient use of the resources available on modern graphics cards which mainly limit the amount of data that can be visualized. The implementation was successfully tested on a tiled display comprised of 25 compute nodes driving 50 LCD panels.

Evaluation of large display interaction using smart phones

Visual analytics, “the science of analytical reasoning facilitated by visual interactive interfaces” [5], puts high demands on the applications visualization as well as interaction capabilities. Due to their size large high-resolution screens have become popular display devices, especially when used in collaborative data analysis scenarios. However, traditional interaction methods based on combinations of computer mice and keyboards often do not scale to the number of users or the size of the display. Modern smart phones featuring multi-modal input/output and considerable memory offer a way to address these issues. In the last couple of years they have become common everyday life gadgets. In this paper we conduct an extensive user study comparing the experience of test candidates when using traditional input devices and metaphors with the one when using new smart phone based techniques, like multi-modal drag and tilt. Candidates were asked to complete various interaction tasks relevant for most applications on a large, monitor-based, high-resolution tiled wall system. Our study evaluates both user performance and satisfaction, identifying strengths and weaknesses of the researched interaction methods in specific tasks. Results reveal good performance of users in certain tasks when using the new interaction techniques. Even first-time users were able to complete a task faster with the smart phone than with traditional devices.

Evaluation of Mobile Phones for Large Display Interaction

Large displays have become more and more common in the last few years. While interaction with these displays can be conducted using standard methods such as computer mouse and keyboard, this approach causes issues in multi-user environments, where the various conditions for providing multiple keyboards and mice, together with the facilities to employ them, cannot be met. To solve this problem, interaction using mobile phones was proposed by several authors. Previous solutions were specialized interaction metaphors only for certain applications. To gain more insight into general interaction patterns realizable with smart phones, we created a set of general test cases using a well-known taxonomy for interactions. These test cases were then evaluated in a user study, comparing smart phone usage against the traditional keyboard/mouse-combination. Results (time and user satisfaction) show strengths and weaknesses when using the new interaction with the smart phone. With further evaluations we draw conclusions on how to improve large display interaction using smart phones in general.

iGreen: non-formal modelling in practice

Motivation -- In the following we describe the development of new visualization and interaction metaphors in the context of iGreen. iGreen is a project dealing with knowledge management in the agricultural industry. We give two example scenarios in which formal modelling cannot be applied easily. Research approach -- The number of actors participating in iGreen is high and encompasses different levels of background knowledge, project expectations, and technical affinities. Over the course of time objective targets gradually changed due to an increased understanding of processes within the project and new unforeseen technical opportunities that turned up in the area of mobile computing. The methods developed had to be accessible for a wide variety of potential users and offer opportunities for interactive data exploration on various hardware platforms. Findings/Design -- The project dynamic made conventional software development strategies hard to apply. The demand for more flexible methods to design visualization techniques and interaction metaphors portable and scalable to different sized hardware platforms increased during the project. Research limitations/Implications -- The target group of users for techniques developed in iGreen is highly related to practice. In order to overcome adaption resistances and replace traditional, mostly manual, workflows, the methods had to be highly intuitive, reliable, and offer steep learning curves. Take away message -- Two application areas in the field of agricultural industry are discussed for which visualization and interaction techniques have been developed. Both examples represent different ends of a wide spectrum of potential target platforms that had to be served.

SEE MORE: Improving the Usage of Large Display Environments

Truly seamless tiled displays and stereoscopic large high-resolution displays are among the top research challenges in the area of large displays. In this paper we approach both topics by adding an additional projector to a tiled display scenario as well as to a stereoscopic environment. In both cases, we have developed new focus+context screen approaches: a multiple foci plus context metaphor in the tiled display setup and a 2D+3D focus+context metaphor in the stereoscopic scenario.

D.I.P. – A Digital Interactive Pinboard with Support for Smart Device Interaction

Smart phone devices are more popular than ever and becauseof their processing power able to deal with almost any kind of multimedia content, i.e., videos, audio, images,and text documents. Files ar ...