Michal Koutek

IntenSelect: using dynamic object rating for assisting 3D object selection

We present IntenSelect, a novel selection technique that dynamically assists the user in the selection of 3D objects in Virtual Environments. Ray-casting selection is commonly used, although it has limited accuracy and can be problematic in more difficult situations where the intended selection object is occluded or moving. Selection-byvolume techniques, which extend normal ray-casting, provide error tolerance to cope with the limited accuracy. However, these extensions generally are not usable in the more complex selection situations.We have devised a new selection-by-volume technique to create a more flexible selection technique which can be used in these situations. To achieve this, we use a new scoring function to calculate the score of objects, which fall within a user controlled, conic selection volume. By accumulating these scores for the objects, we obtain a dynamic, time-dependent, object ranking. The highest ranking object, or active object, is indicated by bending the otherwise straight selection ray towards it. As the selection ray is effectively snapped to the object, the user can now select the object more easily. Our user tests indicate that IntenSelect can improve the selection performance over ray-casting, especially in the more difficult cases of small objects. Furthermore, the introduced time-dependent object ranking proves especially useful when objects are moving, occluded and/or cluttered. Our simple scoring scheme can be easily extended for special purpose interaction such as widget or application specific interaction functionality, which creates new possibilities for complex interaction behavior.

A statistical approach to the life cycle analysis of cumulus clouds selected in a virtual reality environment

In this study, a new method is developed to investigate the entire life cycle of shallow cumuli in large eddy simulations. Although trained observers have no problem in distinguishing the different life stages of a cloud, this process proves difficult to automate, because cloud-splitting and cloud-merging events complicate the distinction between a single system divided in several cloudy parts and two independent systems that collided. Because the human perception is well equipped to capture and to make sense of these time-dependent three-dimensional features, a combination of automated constraints and human inspection in a three-dimensional virtual reality environment is used to select clouds that are exemplary in their behavior throughout their entire life span. Three specific cases (ARM, BOMEX, and BOMEX without large-scale forcings) are analyzed in this way, and the considerable number of selected clouds warrants reliable statistics of cloud properties conditioned on the phase in their life cycle. The most dominant feature in this statistical life cycle analysis is the pulsating growth that is present throughout the entire lifetime of the cloud, independent of the case and of the large-scale forcings. The pulses are a self-sustained phenomenon, driven by a balance between buoyancy and horizontal convergence of dry air. The convective inhibition just above the cloud base plays a crucial role as a barrier for the cloud to overcome in its infancy stage, and as a buffer region later on, ensuring a steady supply of buoyancy into the cloud.

Towards intuitive exploration tools for data visualization in VR

In this paper we present a basic set of intuitive exploration tools for the data visualization in a Virtual Environment on the Responsive Workbench. First, we introduce the Plexipad, a transparent acrylic panel which allows two-handed interaction in combination with a stylus. After a description of various interaction scenarios with these two devices, we present a basic set of interaction tools, which support the user in the process of exploring volumetric datasets. Besides the interaction tools for navigation and selection we present tools that are closely coupled with probing tools. These interactive probing tools are used as input for complex visualization tools and for performing virtual measurements. We illustrate the use of our tools in two applications from different research areas which use volumetric and particle data.

Spring-based manipulation tools for virtual environments

In this paper we present new tools for user interaction with virtual worlds, to bring more natural behavior into the manipulation of objects in virtual environments. We present some principles of physically realistic behavior of virtual objects and a set of user input techniques suitable for semi-immersive VR devices such as the Responsive Workbench. We introduce springs, spring-forks and spring-probes as new tools for assisting direct manipulation of objects in VEs. In this paper we focus on controlling rotational motions.

Virtual spring manipulators for particle steering in molecular dynamics on the responsive workbench

In this paper we present new virtual spring manipulator-based tools for steering particles in molecular dynamics simulations in virtual environments. We briefly overview the MolDRIVE system, our visualization and computational steering environment for molecular dynamics real-time simulations, which is the platform for our particle steering implementation.Our study concentrates on visual feedback tools. We compare a basic virtual particle steering method with two other methods using a spring manipulator. The first just creates a visual feedback of a flexible connection between the users interaction device and the steered particle, while the second technique creates a visual illusion of force feedback. The user can, through the spring manipulator, exert a force on the manipulated particle in the MD simulation. All presented particle steering tools are intuitive and easy to use.

Hybrid interfaces in VEs: intent and interaction

Hybrid user interfaces (UIs) integrate well-known 2D user interface elements into the 3D virtual environment, and provide a familiar and portable interface across a variety of VR systems. However, their usability is often reduced by accuracy and speed, caused by inaccuracies in tracking and a lack of constraints and feedback. To ease these difficulties often large widgets and bulky interface elements must be used, which, at the same time, limit the size of the 3D workspace and restrict the space where other supplemental 2D information can be displayed. In this paper, we present two developments addressing this problem: supportive user interaction and a new implementation of a hybrid interface. First, we describe a small set of tightly integrated 2D windows we developed with the goal of providing increased flexibility in the UI and reducing UI clutter. Next we present extensions to our supportive selection technique, IntenSelect. To better cope with a variety of VR and UI tasks, we extended the selection assistance technique to include direct selection, spring-based manipulation, and specialized snapping behavior. Finally, we relate how the effective integration of these two developments eases some of the UI restrictions and produces a more comfortable VR experience.

Flexible Abstraction Layers for VR Application Development

The development of domain-specific virtual reality applications is often a slow and laborious process. The integration of the domain-specific functionality in an interactive Virtual Environment requires close collaboration between domain expert and VR developer, as well as the integration of domain-specific data and software in a VR application. The software environment needs to support the entire development process and software life cycle, from the early stages of iterative, rapid prototyping to a final end-user application. In this paper, we propose the use of flexible abstraction layers in the form of a dynamic scripting language, which act as the glue between VR system components and external software libraries and applications. First, we discuss the motivation and potential of our approach, after which we overview related approaches. Then, we describe the integration of a Python interpreter in our VR toolkit. The potential of our integration approach is demonstrated by rapid prototyping features, the flexible extension of core functionality and the integration of an external toolkit. We conclude with an overview of implications our approach has for the future development of new framework features and application integration

Feature tracking in VR for cumulus cloud life-cycle studies

Feature tracking in large data sets is traditionally an off-line, batch processing operation while virtual reality typically focuses on highly interactive tasks and applications. This paper presents an approach that uses a combination of off-line preprocessing and interactive visualization in VR to simplify and speed up the identification of interesting features for further study. We couch the discussion in terms of our collaborative research on using virtual reality for cumulus cloud life-cycle studies, where selecting suitable clouds for study is simple for the skilled observer but difficult to formalize. The preprocessing involves identifying individual clouds within the data set through a 4D connected components algorithm, and then saving isosurface, bounding box, and volume information. This information is then interactively visualized in our VR Cloud Explorer with various tools and information displays to identify the most interesting clouds. In a small pilot study, reasonable performance, both in the preprocessing phase and the visualization phase, has been measured.

Parallel particle rendering: a performance comparison between Chromium and Aura

In the fields of high performance computing and distributed rendering, there is a great need for a flexible and scalable architecture that supports coupling of parallel simulations to commodity visualization clusters. The most popular architecture that allows such flexibility, called Chromium, is a parallel implementation of OpenGL. It has sufficient performance on applications with static scenes, but in case of more dynamic content this approach often fails. We have developed Aura, a distributed scene graph library, which allows optimized performance for both static and more dynamic scenes. In this paper we compare the performance of Chromium and Aura. For our performance tests, we have selected a dynamic particle system application, which reveals several issues with the Chromium approach of implementing the OpenGL API. Because our distributed scene graph architecture was designed with a different approach, the test results will show that it performs better on this application.

Dynamics in interaction on the responsive workbench

In this paper we present a different view of user interaction with virtual worlds. We start from the question: how can we bring more natural object behavior into virtual environments? Currently, objects in VR applications often behave in a very un-natural way. Incorporation of physical laws in the virtual environment, together with monitoring natural user actions and behavior is desirable.We present some principles of physically more realistic behavior of virtual objects and a set of user input techniques suitable for semi-immersive VR devices such as the Responsive Workbench. We introduce springs as a new tool for assisting direct manipulation of objects in VEs.