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Feature Article

Exploring Ocean Flow Models With a Multitouch 3D Interface

By Dr. Thomas Butkiewicz
Research Scientist
Center for Coastal and Ocean Mapping
University of New Hampshire
Durham, New Hampshire

Due to the constant increases in the complexity and amount of available hydrographic data, there is a real need to make such large data sets understandable.

The Center for Coastal and Ocean Mapping (CCOM) at the University of New Hampshire began in January 2011 to develop an experimental environment for exploratory visual analysis of ocean flow models in its Data Visualization Research Lab. Through a combination of established visualization techniques and interactive hardware, it gives domain scientists the ability to extract new insights from the results of ocean flow simulations, which have traditionally been challenging to visualize and analyze.

Modern ocean flow simulations are providing ever greater depth resolution in ocean current models. Unfortunately, these inherently 3D models are too often visualized one slice at a time using traditional 2D methods. By focusing on flow patterns one depth at a time, the user loses overall context as to how particular patterns relate to those above and below. By viewing in 3D, users can simultaneously focus on flow patterns at any depth range, while preserving the context of how those patterns relate to the rest of the model. Furthermore, it naturally reveals the complexity of flow patterns with depth-dependent structures.

Challenges in 3D Flow Visualization
Visualizing 3D flow data presents many challenges. One of the most significant is depth ambiguity; it can be hard to tell whether nearby objects are in front of, or behind each other. CCOM's system utilizes stereoscopic rendering, in which each eye is presented with a slightly different image, generated from offset viewing positions, to produce a true 3D image, giving the viewer proper disparity-based depth cues. This ensures that the 3D positions of data items are correctly perceived, thus simplifying perception of the relationships between them. This is especially relevant when dealing with ocean currents, as they can often loop around or cross over at different depths, making it difficult (without stereoscopic 3D) to differentiate the paths of particles caught in visually overlapping currents.

Another major challenge when working in 3D is interactions such as selection and navigation. In 2D, navigation is as simple as scrolling around and zooming in and out. In 3D, users must be able to reposition their viewpoint to look at any part of the model, from any direction. CCOM's system uses multitouch gestures to allow the user to quickly change viewpoints, examine areas of interest, select data and manipulate the visualization tools.

Multitouch 3D Interface
CCOM's visualization system employs a combination of off-the-shelf technologies. Similar environments, mostly using projectors, have been constructed before, but this particular design differs in its relatively low cost, lack of wired devices and minimal space requirements, allowing deployment aboard research vessels and in standard office settings.

While 3D and multitouch monitors are readily available, no existing monitors implement both features in an suitable, integrated fashion. CCOM's system uses a custom combination of multitouch overlays from PQ Labs directly mounted on uncased LCD panels extracted from monitors designed for 3D video games (e.g., Acer HN274H). NVIDIA's 3D Vision provides active LCD shutter glasses and an infrared sync emitter.

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Dr. Thomas Butkiewicz specializes in creating highly interactive geospatial visualizations and experimenting with exploratory visual analysis techniques. His research interests also include multitouch and other natural interfaces, virtual reality, stereoscopic displays, image processing and computer vision.

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