Dane Coffey

Interactive Slice WIM: Navigating and Interrogating Volume Data Sets Using a Multisurface, Multitouch VR Interface

We present Interactive Slice World-in-Miniature (WIM), a framework for navigating and interrogating volumetric data sets using an interface enabled by a virtual reality environment made of two display surfaces: an interactive multitouch table, and a stereoscopic display wall. The framework addresses two current challenges in immersive visualization: 1) providing an appropriate overview+detail style of visualization while navigating through volume data, and 2) supporting interactive querying and data exploration, i.e., interrogating volume data. The approach extends the WIM metaphor, simultaneously displaying a large-scale detailed data visualization and an interactive miniature. Leveraging the table+wall hardware, horizontal slices are projected (like a shadow) down onto the table surface, providing a useful 2D data overview to complement the 3D views as well as a data context for interpreting 2D multitouch gestures made on the table. In addition to enabling effective navigation through complex geometries, extensions to the core Slice WIM technique support interacting with a set of multiple slices that persist on the table even as the user navigates around a scene and annotating and measuring data via points, paths, and volumes specified using interactive slices. Applications of the interface to two volume data sets are presented, and design decisions, limitations, and user feedback are discussed.

Toward mixed method evaluations of scientific visualizations and design process as an evaluation tool

In this position paper we discuss successes and limitations of current evaluation strategies for scientific visualizations and argue for embracing a mixed methods strategy of evaluation. The most novel contribution of the approach that we advocate is a new emphasis on employing design processes as practiced in related fields (e.g., graphic design, illustration, architecture) as a formalized mode of evaluation for data visualizations. To motivate this position we describe a series of recent evaluations of scientific visualization interfaces and computer graphics strategies conducted within our research group. Complementing these more traditional evaluations our visualization research group also regularly employs sketching, critique, and other design methods that have been formalized over years of practice in design fields. Our experience has convinced us that these activities are invaluable, often providing much more detailed evaluative feedback about our visualization systems than that obtained via more traditional user studies and the like. We believe that if design-based evaluation methodologies (e.g., ideation, sketching, critique) can be taught and embraced within the visualization community then these may become one of the most effective future strategies for both formative and summative evaluations.

Vortex formation and instability in the left ventricle

We carry out high-resolution direct numerical simulation to investigate the vortex dynamics of the diastolic phase of blood flow in an anatomic left ventricle (LV) chamber at physiologic conditions. We reconstruct the anatomic left heart geometry from magnetic resonance imaging data of a healthy subject. The details of the LV kinematic model and the computational setup can be found in Le,1 and Le and Sotiropoulos.2 In the Gallery of Fluid Motion video, we describe in detail the three-dimensional formation and subsequent instability of the mitral vortex ring, which is initially formed during early diastolic filling (E-wave). During the initial phase of the E-wave, the simulations reveal the existence of a well-defined vortex ring formed at the edge of the mitral orifice. After the E-wave, this vortex ring is fully formed and propagates toward the LV apex. The subsequent structure and fate of the ring is visualized in Fig. ​Fig.11 in terms of an instantaneous iso-surface of vorticity magnitude colored with helicity contours. As seen in this figure, the initially circular ring becomes inclined and propagates toward the LV posterior wall. Vortex-wall interactions induce the formation of secondary vortex tubes, denoted as trailing vortex tubes, that grow from the wall and wrap around the primary ring. These trailing vortex tubes begin to interact with and destabilize the mitral vortex ring through complex twisting core instabilities, which are evident in Figs. ​Figs.1b,1b, ​,1c,1c, ​,22. Figure 1 The mitral vortex ring visualized by an iso-surface of vorticity magnitude colored by helicity density at two instants in time during diastolic filling. (a) and (b) show the vortical structures as viewed from the apex of the heart. (c) shows the anterior-posterior ... Figure 2 Snapshots taken from a virtual reality visualization depicting the impingement of the mitral vortex ring on the left ventricular wall during late diastolic filling. The mitral vortex ring is visualized by an iso-surface of vorticity magnitude. Left: anterior/posterior ... As the mitral vortex ring advances toward the apex, its initially circular shape (Fig. ​(Fig.1a)1a) is deformed as it is strained laterally to acquire an elliptical shape as seen in Fig. ​Fig.1b.1b. Both the twisting of the secondary vortex tubes around the rings core as well as the growth of twisting instabilities along the rings core intensify. At the end of diastole (see Fig. ​Fig.2),2), the vortex ring impinges on the LV wall and begins to break down into small-scale structures. The dynamics of the mitral vortex ring uncovered by our simulations is broadly similar to the dynamics of vortex rings from inclined nozzles.3 In both cases, the vortex evolution and subsequent breakdown is dominated by the growth of secondary vortex tubes due to wall-vortex and vortex-vortex interaction, the wrapping of these tubes around the core of the primary ring, and the growth of complex, twisting instability modes.3 This work was supported by National of Institutes of Health (NIH) Grant RO1-HL-07262 and the Minnesota Supercomputing Institute. We thank Ajit Yoganathan and the members of the Georgia Tech Cardiovascular Fluid Mechanics Laboratory for providing us with the anatomic LV geometry used in this study. We thank Dr. Minh X. Nguyen at Microsoft Corporation for the fruitful flow visualization discussion. The first author is partially supported by a fellowship from Vietnam Education Foundation.

Low cost VR meets low cost multi-touch

This paper presents the design, implementation, and lessons learned from developing a multi-surface VR visualization environment. The environment combines a head-tracked vertical VR display with a multi-touch table display. An example user interface technique called Shadow Grab is presented to demonstrate the potential of this design. Extending recent efforts to make VR more accessible to a broad audience, the work makes use of low-cost VR components and demonstrates how these can be combined in a multiple display configuration with lowcost multi-touch hardware, drawing upon knowledge from the rapidly growing low-cost/do-it-yourself multi-touch community. Details needed to implement the interactive environment are provided along with discussion of the limitations of the current design and the potential of future design variants.

Visualizing Motion Data in Virtual Reality: Understanding the Roles of Animation, Interaction, and Static Presentation

We present a study of interactive virtual reality visualizations of scientific motions as found in biomechanics experiments. Our approach is threefold. First, we define a taxonomy of motion visualizations organized by the method (animation, interaction, or static presentation) used to depict both the spatial and temporal dimensions of the data. Second, we design and implement a set of eight example visualizations suggested by the taxonomy and evaluate their utility in a quantitative user study. Third, together with biomechanics collaborators, we conduct a qualitative evaluation of the eight example visualizations applied to a current study of human spinal kinematics. Results suggest that visualizations in this style that use interactive control for the time dimension of the data are preferable to others. Within this category, quantitative results support the utility of both animated and interactive depictions for space; however, qualitative feedback suggest that animated depictions for space should be avoided in biomechanics applications.

Force Brushes: Progressive Data-Driven Haptic Selection and Filtering for Multi-Variate Flow Visualizations

We present Force Brushes, a haptic-based interaction technique for controlled selection in multi-variate flow visualizations. Force Brushes addresses the difficult task of volumetric selection and filtering by rendering haptic constraints that allow scientists to snap directly to proxy geometry, such as streamlines, to select regions of interest and then progressively filter the selection using a data-driven approach. Using progressive brushing actions with multiple variables, a user has the potential to explore volumetric data in a more immediate, fluid, and controllable way guided by the underlying data.

A Process for Design, Verification, Validation, and Manufacture of Medical Devices Using Immersive VR Environments

This paper presents a framework and detailed vision for using immersive virtual reality (VR) environments to improve the design, verification, validation, and manufacture of medical devices. Major advances in medical device design and manufacture currently require extensive and expensive product cycles that include animal and clinical trials. The current design process limits opportunities to thoroughly understand and refine current designs and to explore new high-risk, high-payoff designs. For the past 4 years, our interdisciplinary research group has been working toward developing strategies to dramatically increase the role of simulation in medical device engineering, including linking simulations with visualization and interactive design. Although this vision aligns nicely with the stated goals of the FDA and the increasingly important role that simulation plays in engineering, manufacturing, and science today, the interdisciplinary expertise needed to realize a simulation-based visual design environment for real-world medical device design problems makes implementing (and even generating a system-level design for) such a system extremely challenging. In this paper, we present our vision for a new process of simulation-based medical device engineering and the impact it can have within the field. We also present our experiences developing the initial components of a framework to realize this vision and applying them to improve the design of replacement mechanical heart valves. Relative to commercial software packages and other systems used in engineering research, the vision and framework described are unique in the combined emphasis on 3D user interfaces, ensemble visualization, and incorporating state-of the-art custom computational fluid dynamics codes. We believe that this holistic conception of simulation-based engineering, including abilities to not just simulate with unprecedented accuracy but also to visualize and interact with simulation results, is critical to making simulation-based engineering practical as a tool for major innovation in medical devices. Beyond the medical device arena, the framework and strategies described may well generalize to simulation-based engineering processes in other domains that also involve simulating, visualizing, and interacting with data that describe spatially complex time-varying phenomena.

Shadow WIM: a multi-touch, dynamic world-in-miniature interface for exploring biomedical data

Advances in high-performance (supercomputer) simulations are revolutionizing biomedical research. Figure 1 shows a visualiazation of data from a cutting-edge computational fluid dynamics (CFD) simulation of blood flow through a replacement heart valve. Our collaborators in medical device design hope to use these data as part of a new approach to redesigning the valve hinging mechanism, ultimately improving the longevity of these devices. Biomedical engineers face significant challenges in exploring and understanding these data.

Optimizing Design with Extensive Simulation Data: A Case Study of Designing a Vacuum-Assisted Biopsy Tool

Design by Dragging (DBD) [1] is a virtual design tool, which displays three-dimensional (3D) visualizations of many simulation results obtained by sampling a large design space and ties this visual display together with a new user interface. The design space is explored through mouse-based interactions performed directly on top of the 3D data visualizations. Our previous study [1] introduced the realization of DBD with a simplistic example of biopsy needle design under a static bending force. This paper considers a realistic problem of designing a vacuum-assisted biopsy (VAB) needle that brings in more technical challenges to include dynamic tissue reaction forces, nonlinear tissue deformation, and progressive tissue damage in an integrated visualization with design suggestions. The emphasis is placed on the inverse design strategy in DBD, which involves clicking directly on a stress (or other output field parameter) contour and dragging it to a new (usually preferable) position on the contour. Subsequently, the software computes the best fit for the design variables for generating a new output stress field based on the user input. Three cases demonstrated how the inverse design can assist users in intuitively and interactively approaching desired design solutions. This paper illustrates how virtual prototyping may be used to replace (or reduce reliance on) purely experimental trial-and-error methods for achieving optimal designs.

A user study to understand motion visualization in virtual reality

Studies of motion are fundamental to science. For centuries, pictures of motion have factored importantly in making scientific discoveries possible. Today, there is perhaps no tool more powerful than interactive virtual reality (VR) for conveying complex space-time data to scientists, doctors, and others; however, relatively little is known about how to design virtual environments in order to best facilitate these analyses. In designing virtual environments for presenting scientific motion data (e.g., 4D data captured via medical imaging or motion tracking) our intuition is most often to “reanimate” these data in VR, displaying moving virtual bones and other 3D structures in virtual space as if the viewer were watching the data being collected in a biomechanics lab. However, recent research in other contexts suggests that although animated displays are effective for presenting known trends, static displays are more effective for data analysis.