The Cosmic Explorer
Collaborators: Carolina Cruz-Neira (University of Illinois at Chicago), Michael Norman, Deyang Song
(National Center for Supercomputing Applications)
The Cosmic Explorer is a research tool for exploring the stages of the
evolution of the universe. We visualize the result of numerical simulations
to allow the exploration of the formation of the universe, astrophysical
jets, and colliding galaxies. This application, originally written for
the BOOM, is being ported to the CAVE.
CAVE Visualization
Figure 2.1 
Figure 2.2
In the CAVE visualization, each galaxy is depicted as a point in three
dimensional space; the color of each point represents the age of the
galaxy (blue being the oldest, yellow being the youngest). Figures 2.1 -
2.4 show several stages of the Universe's evolution.
Other representations for the galaxies, such as cubes, tetrahedrons or
textured polygons, were also considered but rejected because they compromised
the rendering speed or did not contribute additional information to the experience.
We settled for the single pixel point representation because it was the
fastest and most intuitive model.
Figure 2.3 
Figure 2.4
The animation shows the evolution of the Universe since the Big Bang.
It starts as a single mass that explodes and expands in front of the
viewers until it completely surrounds them, filling the CAVE space.
The user can pause the animation and travel through the data to explore
far away galaxies or step back to view the whole universe structure from
a distance.
Discussion
The Cosmic Explorer is a good example of a human-oriented paradigm for
exploring large data sets with spatial and temporal information. We allow
users to explore the simulation data as they might explore a physical place.
This application received a very positive response from both scientists and
the general public. Standing among the galaxies as they start to cluster
is a dramatic experience. The effects of the clustering galaxies were strongly
depicted in the CAVE because of the panoramic view provided by
the surrounding projection screens, which offered an Omnimax-like experience.
Memory requirements were major concerns when operating the Cosmic Explorer. The
visualization involved a large data set of 30 Mbytes, which is only one-tenth
of the actual simulation data. In the current implementation of the
CAVE, we have to load the entire data set in memory for the interactive
experience. In order to visualize the complete simulation data set, we would
need at least 300 Mbytes of RAM! Large datasets are common across many
simulations. Techniques to manipulate and select portions of data for
CAVE display will have to be developed.
Additional functions such as volume selection, successive refinement of the
images and VCR-like controls would be beneficial to improve the usability
of the application for further astrophysical research.
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