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Todays Virtual Environment frameworks use scene graphs to represent virtual worlds. We believe that this is a proper technical approach, but a VE framework should try to model its application area as accurate as possible. Therefore a scene graph is not the best way to represent a virtual world. In this paper we present an easily extensible model to describe entities in the virtual world. Further on we show how this model drives the design of our VE framework and how it is integrated.
"Visual Computing" (VC) fasst als hochgradig aktuelles Forschungsgebiet verschiedene Bereiche der Informatik zusammen, denen gemeinsam ist, dass sie sich mit der Erzeugung und Auswertung visueller Signale befassen. Im Fachbereich Informatik der FH Bonn-Rhein-Sieg nimmt dieser Aspekt eine zentrale Rolle in Lehre und Forschung innerhalb des Studienschwerpunktes Medieninformatik ein. Drei wesentliche Bereiche des VC werden besonders in diversen Lehreinheiten und verschiedenen Projekten vermittelt: Computergrafik, Bildverarbeitung und Hypermedia-Anwendungen. Die Aktivitäten in diesen drei Bereichen fließen zusammen im Kontext immersiver virtueller Visualisierungsumgebungen.
In dieser Arbeit wird eine Methode zur Darstellung und Generierung von natürlich wirkendem Bewuchs auf besonders großen Arealen und unter Berücksichtigung ökologischer Faktoren vorgestellt. Die Generierung und Visualisierung von Bewuchs ist aufgrund der Komplexität biologischer Systeme und des Detailreichtums von Pflanzenmodellen ein herausforderndes Gebiet der Computergrafik und ermöglicht es, den Realismus von Landschaftsvisualisierungen erheblich zu steigern. Aufbauend auf [DMS06] wird bei Silva der Bewuchs so generiert, dass die zur Darstellung benötigten Wang-Kacheln und die mit ihnen assoziierten Teilverteilungen wiederverwendet werden können. Dazu wird ein Verfahren vorgestellt, um Poisson Disk Verteilungen mit variablen Radien auf nahtlosen Wang-Kachelmengen ohne rechenintensive globale Optimierung zu erzeugen. Durch die Einbeziehung von Nachbarschaften und frei konfigurierbaren Generierungspipelines können beliebige abiotische und biotische Faktoren bei der Bewuchsgenerierung berücksichtigt werden. Die durch Silva auf Wang-Kacheln erzeugten Pflanzenverteilungen ermöglichen, die darauf aufgebauten beschleunigenden Datenstrukturen bei der Visualisierung wieder zu verwenden. Durch Multi-Level Instancing und eine Schachtelung von Kd-Bäumen ist eine Visualisierung von großen bewachsenen Arealen mit geringen Renderzeiten und geringem Memoryfootprint von Hunderten Quadratkilometern Größe möglich.
In diesem Beitrag wird der interaktive Volumenrenderer Volt für die NVIDIA CUDA Architektur vorgestellt. Die Beschleunigung wird durch das Ausnutzen der technischen Eigenschaften des CUDA Device, durch die Partitionierung des Algorithmus und durch die asynchrone Ausführung des CUDA Kernels erreicht. Parallelität wird auf dem Host, auf dem Device und zwischen Host und Device genutzt. Es wird dargestellt, wie die Berechnungen durch den gezielten Einsatz der Ressourcen effizient durchgeführt werden. Die Ergebnisse werden zurückkopiert, so dass der Kernel nicht auf dem zur Anzeige bestimmten Device ausgeführt werden muss. Synchronisation der CUDA Threads ist nicht notwendig.
The steadily decreasing prices of display technologies and computer graphics hardware contribute to the increasing popularity of multiple-display environments, like large, high-resolution displays. It is therefore necessary that educational organizations give the new generation of computer scientists an opportunity to become familiar with this kind of technology. However, there is a lack of tools that allow for getting started easily. Existing frameworks and libraries that provide support for multi-display rendering are often complex in understanding, configuration and extension. This is critical especially in educational context where the time that students have for their projects is limited and quite short. These tools are also rather known and used in research communities only, thus providing less benefit for future non-scientists. In this work we present an extension for the Unity game engine. The extension allows – with a small overhead – for implementation of applications that are apt to run on both single-display and multi-display systems. It takes care of the most common issues in the context of distributed and multi-display rendering like frame, camera and animation synchronization, thus reducing and simplifying the first steps into the topic. In conjunction with Unity, which significantly simplifies the creation of different kinds of virtual environments, the extension affords students to build mock-up virtual reality applications for large, high-resolution displays, and to implement and evaluate new interaction techniques and metaphors and visualization concepts. Unity itself, in our experience, is very popular among computer graphics students and therefore familiar to most of them. It is also often employed in projects of both research institutions and commercial organizations; so learning it will provide students with qualification in high demand.
Development and rapid prototyping for large interactive environments like tiled-display walls pose many challenges. One is the heterogeneity of the various applications and libraries. A visual application tailored for a single monitor setup with a certain software environment is difficult to port and distribute to a multi-display, multi-PC setup. As a solution to this problem, we explore the potential of lightweight containerization techniques for distributed interactive applications. In particular, we present how the necessary runtime and build environments including libraries and drivers can be abstracted using the Docker framework. We demonstrate the packing of an existing single-machine GPU-enabled ray tracer inside a container to be used on tiled display walls. The performance measurements reveal that the containerization has a negligible impact on the system’s performance but allows for easy setup, integration, and distribution of complex applications.
Supported by their large size and high resolution, display walls suit well for different collaboration types. However, in order to foster instead of impede collaboration processes, interaction techniques need to be carefully designed, taking into regard the possibilities and limitations of the display size, and their effects on human perception and performance. In this paper we investigate the impact of visual distractors (which, for instance, might be caused by other collaborators' input) in peripheral vision on short-term memory and attention. The distractors occur frequently when multiple users collaborate in large wall display systems and may draw attention away from the main task, as such potentially affecting performance and cognitive load. Yet, the effect of these distractors is hardly understood. Gaining a better understanding thus may provide valuable input for designing more effective user interfaces. In this article, we report on two interrelated studies that investigated the effect of distractors. Depending on when the distractor is inserted in the task performance sequence, as well as the location of the distractor, user performance can be disturbed: we will show that distractors may not affect short term memory, but do have an effect on attention. We will closely look into the effects, and identify future directions to design more effective interfaces.
In this article, we report on challenges and potential methodologies to support the design and validation of multisensory techniques. Such techniques can be used for enhancing engagement in immersive systems. Yet, designing effective techniques requires careful analysis of the effect of different cues on user engagement. The level of engagement spans the general level of presence in an environment, as well as the specific emotional response to a set trigger. Yet, measuring and analyzing the actual effect of cues is hard as it spans numerous interconnected issues. In this article, we identify the different challenges and potential validation methodologies that affect the analysis of multisensory cues on user engagement. In doing so, we provide an overview of issues and potential validation directions as an entry point for further research. The various challenges are supported by lessons learned from a pilot study, which focused on reflecting the initial validation methodology by analyzing the effect of different stimuli on user engagement.
We propose a high-performance GPU implementation of Ray Histogram Fusion (RHF), a denoising method for stochastic global illumination rendering. Based on the CPU implementation of the original algorithm, we present a naive GPU implementation and the necessary optimization steps. Eventually, we show that our optimizations increase the performance of RHF by two orders of magnitude when compared to the original CPU implementation and one order of magnitude compared to the naive GPU implementation. We show how the quality for identical rendering times relates to unfiltered path tracing and how much time is needed to achieve identical quality when compared to an unfiltered path traced result. Finally, we summarize our work and describe possible future applications and research based on this.
Ray Tracing, accurate physical simulations with collision detection, particle systems and spatial audio rendering are only a few components that become more and more interesting for Virtual Environments due to the steadily increasing computing power. Many components use geometric queries for their calculations. To speed up those queries spatial data structures are used. These data structures are mostly implemented for every problem individually resulting in many individually maintained parts, unnecessary memory consumption and waste of computing power to maintain all the individual data structures. We propose a design for a centralized spatial data structure that can be used everywhere within the system.
We present an interactive system that uses ray tracing as a rendering technique. The system consists of a modular Virtual Reality framework and a cluster-based ray tracing rendering extension running on a number of Cell Broadband Engine-based servers. The VR framework allows for loading rendering plugins at runtime. By using this combination it is possible to simulate interactively effects from geometric optics, like correct reflections and refractions.
We present fast complete rebuild strategies, as well as adapted intelligent local update strategies for acceleration data structures for interactive ray tracing environments. Both approaches can be combined. Although the proposed strategies could be used with other data structures and architectures as well, they are currently tailored to the Bounding Interval Hierarchy on the Cell chip.
Head-mounted displays (HMDs) with integrated eye trackers have opened up a new realm for gaze-contingent rendering. The accurate estimation of gaze depth is essential when modeling the optical capabilities of the eye. Most recently multifocal displays are gaining importance, requiring focus estimates to control displays or lenses. Deriving the gaze depth solely by sampling the scene's depth at the point-of-regard fails for complex or thin objects as eye tracking is suffering from inaccuracies. Gaze depth measures using the eye's vergence only provide an accurate depth estimate for the first meter. In this work, we combine vergence measures and multiple depth measures into feature sets. This data is used to train a regression model to deliver improved estimates. We present a study showing that using multiple features allows for an accurate estimation of the focused depth (MSE<0.1m) over a wide range (first 6m).
An electronic display often has to present information from several sources. This contribution reports about an approach, in which programmable logic (FPGA) synchronises and combines several graphics inputs. The application area is computer graphics, especially rendering of large 3D models, which is a computing intensive task. Therefore, complex scenes are generated on parallel systems and merged to give the requested output image. So far, the transportation of intermediate results is often done by a local area network. However, as this can be a limiting factor, the new approach removes this bottleneck and combines the graphic signals with an FPGA.
This paper describes FGPA-based image combining for parallel graphics systems. The goal of our current work is to reduce network traffic and latency for increasing performance in parallel visualization systems. Initial data distribution is based on a common ethernet network whereas image combining and returning differs to traditional parallel rendering methods. Calculated sub-images are grabbed directly from the DVI-Ports for fast image compositing by a FPGA-based combiner.
In this paper we present an approach to efficiently trace single rays on the Cell Processor, instead of using ray packets. To benefit from the performance of this processor, a data structure is chosen which allows traversal without excessive accesses to main memory. Together with careful optimization for SIMD processing, a performance comparable to a packet based ray tracer, running on the same hardware, is achieved. In special cases, when the coherency of the traced rays get very low, it even outperforms the packet based approach.
In Mixed Reality (MR) Environments, the user's view is augmented with virtual, artificial objects. To visualize virtual objects, the position and orientation of the user's view or the camera is needed. Tracking of the user's viewpoint is an essential area in MR applications, especially for interaction and navigation. In present systems, the initialization is often complex. For this reason, we introduce a new method for fast initialization of markerless object tracking. This method is based on Speed Up Robust Features and paradoxically on a traditional marker-based library. Most markerless tracking algorithms can be divided into two parts: an offline and an online stage. The focus of this paper is optimization of the offline stage, which is often time-consuming.
We present our approach to extend a Virtual Reality software framework towards the use for Augmented Reality applications. Although VR and AR applications have very similar requirements in terms of abstract components (like 6DOF input, stereoscopic output, simulation engines), the requirements in terms of hardware and software vary considerably. In this article we would like to share the experience gained from adapting our VR software framework for AR applications. We will address design issues for this task. The result is a VR/AR basic software that allows us to implement interactive applications without fixing their type (VR or AR) beforehand. Switching from VR to AR is a matter of changing the configuration file of the application.
This paper introduces a novel zooming interface deploying a pico projector that, instead of a second visual display, leverages audioscapes for contextual information. The technique enhances current flashlight metaphor approaches, supporting flexible usage within the domain of spatial augmented reality to focus on object or environment-related details. Within a user study we focused on quantifying the projection limitations related to depiction of details through the pico projector and validated the interaction approach. The quantified results of the study correlate pixel density, detail and proximity, which can greatly aid to design more effective, legible zooming interfaces for pico projectors - the study can form an example testbed that can be applied well for testing aberrations with other projectors. Furthermore, users rated the zooming technique using audioscapes well, showing the validity of the approach. The studies form the foundation for extending our work by detailing out the audio-visual approach and looking more closely in the role of real-world features on interpreting projected content.
Rendering techniques for design evaluation and review or for visualizing large volume data often use computationally expensive ray-based methods. Due to the number of pixels and the amount of data, these methods often do not achieve interactive frame rates. A view direction based rendering technique renders the users central field of view in high quality whereas the surrounding is rendered with a level of detail approach depending on the distance to the users central field of view thus giving the opportunity to increase rendering efficiency. We propose a prototype implementation and evaluation of a focus-based rendering technique based on a hybrid ray tracing/sparse voxel octree rendering approach.
We present basho, a light weight and easily extendable virtual environment (VE) framework. Key benefits of this framework are independence of the scene element representation and the rendering API. The main goal was to make VE applications flexible without the need to change them, not only by being independent from input and output devices. As an example, with basho it is possible to switch from local illumination models to ray tracing by just replacing the renderer. Or to replace the graphical representation of the scene elements without the need to change the application. Furthermore it is possible to mix rendering technologies within a scene. This paper emphasises on the abstraction of the scene element representation.
A recent trend in interactive environments are large, ultra high resolution displays (LUHRDs). Compared to other large interactive installations, like the CAVE tm , LUHRDs are usually flat or (slightly) curved and have a significantly higher resolution, offering new research and application opportunities.
This tutorial provides information for researchers and engineers who plan to install and use a large ultra-high resolution display. We will give detailed information on the hardware and software of recently created and established installations and will show the variety of possible approaches. Also, we will talk about rendering software, rendering techniques and interaction for LUHRDs, as well as applications.
We present a system that combines voxel and polygonal representations into a single octree acceleration structure that can be used for ray tracing. Voxels are well-suited to create good level-of-detail for high-frequency models where polygonal simplifications usually fail due to the complex structure of the model. However, polygonal descriptions provide the higher visual fidelity. In addition, voxel representations often oversample the geometric domain especially for large triangles, whereas a few polygons can be tested for intersection more quickly.
