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From the earliest efforts to compute the universe, it was clear that advanced tools and techniques for scientific visualization were essential for making sense of the data pouring out of supercomputers.
Michael Norman, NCSA/Univ. of Illinois,
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At NCSA, cosmologists developed the Cosmic Explorer, a custom visualization tool for controlling the rendering into graphics of large, complex, 3-D data sets resulting from intensive cosmology calculations. This workstation tool also could set the resulting images into motion, generating a series of ground breaking animations.
However, as the importance of doing cosmology simulations over multiple length scales became increasingly evident, it was also clear that yet more advanced visualization capabilities would be needed to explore the resulting data. The reason: this data poses a major visualization challenge since it is five-dimensional: 3 dimensions of space, one of time and one of scale; each must be represented suitably, enabling intuitive exploration of the data by the scientist.
Ideally, the viewer of this data should be able to navigate seamlessly through all five dimensions and be able to interactively control what is seen, in what detail as well as point of view, all of this in realtime. Clearly this demands an environment that goes beyond the traditional workstation. It's no wonder that cosmologists are turning to the technologies underlying virtual environments in order to accomplish their goals. At NCSA, researchers have been adapting the Cosmic Explorer to work with a variety of virtual reality tools, initially with booms, and datagloves.
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More recently, however,the researchers have experimented more elaborate virtual environments such as The CAVE. The CAVE provides the illusion of being inside, not outside the data, enabling scientists not only immerse themselves in their digital universes, but also to move through and interact with them.
Eventually it will be possible to connect interactive multiscale visualization with hierarchical adaptive mesh refinement techniques for computation. This coupling will permit sub-grids to be introduced automatically when more resolution is needed and to view the results immediately.
For example, a viewer might find a region of interest, then select a subvolume and put himself or herself inside, at which point the subvolume takes up the entire virtual space. In this manner, the viewer can "travel" from cluster to cluster of galaxies, an instant later enter a cluster and "witness" galaxies being born. Or perhaps the viewer might want to examine closely a 2-dimensional "slice" of a chosen volume of data, then return to a global view of the entire dataset, viewing it once again from "outside" the simulation box.
The ultimate goal is to develop virtual environments permitting immersive exploration of simulation data and user control or "steering" of the calculations themselves, all in realtime. At this point, navigation, interaction and computation become as one process, allowing digital universes to be modeled and tested as never before.
As a step to this goal, cosmologists at Indiana University, NCSA, Pittsburgh Supercomputing Center and Princeton University successfully demonstrated a multiscale simulation of cosmic evolution at Supercomputing '95, employing the latest computing, high speed communications and virtual reality display technologies. Entitled "Galaxies Collide on the I-WAY: An Example of Wide-Area Collaborative Supercomputing," the demonstration won the "Best Integration of Heterogeneous Applications" award.
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