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Fuchs R.,ETH Zurich | Schindler B.,ETH Zurich | Carnecky R.,ETH Zurich | Waser J.,VRVis Vienna | And 2 more authors.
VMV 2012 - Vision, Modeling and Visualization | Year: 2012

We describe a novel adaptive mesh representation for streak-surfaces. The surface is represented as a mesh of small trees of initial depth zero (treelets). This mesh representation allows for efficient integration, refinement, coarsening and appending of surface patches utilizing the computational capacities of modern GPUs. Integration, refinement, and rendering are strictly separated into effectively parallelizable substeps of the streak-surface integration algorithm. We also describe a sampler framework which unifies the handling of different vector field representations. © 2012 The Eurographics Association.

Waser J.,VRVis Vienna | Ribicic H.,VRVis Vienna | Fuchs R.,ETH Zurich | Hirsch C.,VRVis Vienna | And 3 more authors.
IEEE Transactions on Visualization and Computer Graphics | Year: 2011

Flood disasters are the most common natural risk and tremendous efforts are spent to improve their simulation and management. However, simulation-based investigation of actions that can be taken in case of flood emergencies is rarely done. This is in part due to the lack of a comprehensive framework which integrates and facilitates these efforts. In this paper, we tackle several problems which are related to steering a flood simulation. One issue is related to uncertainty. We need to account for uncertain knowledge about the environment, such as levee-breach locations. Furthermore, the steering process has to reveal how these uncertainties in the boundary conditions affect the confidence in the simulation outcome. Another important problem is that the simulation setup is often hidden in a black-box. We expose system internals and show that simulation steering can be comprehensible at the same time. This is important because the domain expert needs to be able to modify the simulation setup in order to include local knowledge and experience. In the proposed solution, users steer parameter studies through the World Lines interface to account for input uncertainties. The transport of steering information to the underlying data-flow components is handled by a novel meta-flow. The meta-flow is an extension to a standard data-flow network, comprising additional nodes and ropes to abstract parameter control. The meta-flow has a visual representation to inform the user about which control operations happen. Finally, we present the idea to use the data-flow diagram itself for visualizing steering information and simulation results. We discuss a case-study in collaboration with a domain expert who proposes different actions to protect a virtual city from imminent flooding. The key to choosing the best response strategy is the ability to compare different regions of the parameter space while retaining an understanding of what is happening inside the data-flow system. © 2011 IEEE.

Schindler B.,ETH Zurich | Fuchs R.,ETH Zurich | Barp S.,VRVis Vienna | Waser J.,VRVis Vienna | And 4 more authors.
IEEE Transactions on Visualization and Computer Graphics | Year: 2012

Room air flow and air exchange are important aspects for the design of energy-efficient buildings. As a result, simulations are increasingly used prior to construction to achieve an energy-efficient design. We present a visual analysis of air flow generated at building entrances, which uses a combination of revolving doors and air curtains. The resulting flow pattern is challenging because of two interacting flow patterns: On the one hand, the revolving door acts as a pump, on the other hand, the air curtain creates a layer of uniformly moving warm air between the interior of the building and the revolving door. Lagrangian coherent structures (LCS), which by definition are flow barriers, are the method of choice for visualizing the separation and recirculation behavior of warm and cold air flow. The extraction of LCS is based on the finite-time Lyapunov exponent (FTLE) and makes use of a ridge definition which is consistent with the concept of weak LCS. Both FTLE computation and ridge extraction are done in a robust and efficient way by making use of the fast Fourier transform for computing scale-space derivatives. © 2012 IEEE.

Waser J.,VRVis Vienna | Fuchs R.,ETH Zurich | Ribicic H.,VRVis Vienna | Schindler B.,ETH Zurich | And 2 more authors.
IEEE Transactions on Visualization and Computer Graphics | Year: 2010

In this paper we present World Lines as a novel interactive visualization that provides complete control over multiple heterogeneous simulation runs. In many application areas, decisions can only be made by exploring alternative scenarios. The goal of the suggested approach is to support users in this decision making process. In this setting, the data domain is extended to a set of alternative worlds where only one outcome will actually happen. World Lines integrate simulation, visualization and computational steering into a single unified system that is capable of dealing with the extended solution space. World Lines represent simulation runs as causally connected tracks that share a common time axis. This setup enables users to interfere and add new information quickly. A World Line is introduced as a visual combination of user events and their effects in order to present a possible future. To quickly find the most attractive outcome, we suggest World Lines as the governing component in a system of multiple linked views and a simulation component. World Lines employ linking and brushing to enable comparative visual analysis of multiple simulations in linked views. Analysis results can be mapped to various visual variables that World Lines provide in order to highlight the most compelling solutions. To demonstrate this technique we present a flooding scenario and show the usefulness of the integrated approach to support informed decision making. © 2006 IEEE.

Ribiclic H.,VRVis Vienna | Waser J.,VRVis Vienna | Gurbat R.,VRVis Vienna | Sadransky B.,VRVis Vienna | Groller M.E.,Vienna University of Technology
IEEE Transactions on Visualization and Computer Graphics | Year: 2012

In a variety of application areas, the use of simulation steering in decision making is limited at best. Research focusing on this problem suggests that most user interfaces are too complex for the end user. Our goal is to let users create and investigate multiple, alternative scenarios without the need for special simulation expertise. To simplify the specification of parameters, we move from a traditional manipulation of numbers to a sketch-based input approach. Users steer both numeric parameters and parameters with a spatial correspondence by sketching a change onto the rendering. Special visualizations provide immediate visual feedback on how the sketches are transformed into boundary conditions of the simulation models. Since uncertainty with respect to many intertwined parameters plays an important role in planning, we also allow the user to intuitively setup complete value ranges, which are then automatically transformed into ensemble simulations. The interface and the underlying system were developed in collaboration with experts in the field of flood management. The real-world data they have provided has allowed us to construct scenarios used to evaluate the system. These were presented to a variety of flood response personnel, and their feedback is discussed in detail in the paper. The interface was found to be intuitive and relevant, although a certain amount of training might be necessary. © 2012 IEEE.

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