Stereoscopic Visualization of Curved Space
The Light group: Werner Benger, Brad Corso, Erin Gillilan, Manuel Tiglio
Presenters at SC05: Edward Seidel and Werner Benger, LSU
In cooperation between CCT
and NCSA.
Black holes are mysterious astrophysical objects which are predicted
by Einstein's theory of general relativity. They are supposed to occur
in nature when a star collapses and extremely strong gravitational
fields form. Einstein's theory describes gravity as the curvature of
space and time, a concept which is not intuitively comprehensible from
our everyday experience. However, curvature of spacetime results in
prominent visual phenomena, which are extremely strong around black
holes. By means of computer graphical simulations we can reproduce
this theoretical effects. Some of these sound counter-intuitive or
even paradoxical when described by words. For instance, the radial
distance to the surface of a black hole is very large (getting
infinite for a hovering [static] observer), but the circumference is
still quite small. Consequently, objects in the vicinity of a black
hole look much more distant than objects behind the black hole.
Using a High Definition Stereo Display device we succeeded to visually communicate
this very behaviour by virtually putting a black hole into an
intuitively known environment. The weird effects of the curvature of
space become visible. This kind of visualization was
presented the first time at Supercomputing 05 and still considered experimental. The
computational effort of creating such images is immense and required a
supercomputer such as SuperMike
at the Center for Computation & Technology
to perform the rendering.
Left eye image
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Right eye image
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Curved space
note the effects of gravitational lensing
on the logo images.
The finite speed of light leads to fronts of light waves expanding
from the point of closest distance to the observer. This effect
does not utilize any special or general relativity at all.
In the general relativistic case light is attracted by the gravity of
the black hole. Light may find more than one path from a source to the
observer, leading to multiple appearances of a certain object.
Objects appear distorted and curved; however, this is just visually the
case, the objects itself remain the same. We can explore this
situation in an Orbit around.
These simulations depict various properties of a gravitational
field; the spatial curvature, the infinite distance to the
horizon, the bending of light around the black hole,
the gravitational time delay and the gradient of time dilation.
These effects will be explained in detail in a forthcoming
paper. Here, we just review some aspects of the presentation
at SC05.
Approaching the Event Horizon
At the culminating end of the presentation
we show a complex combination of all the
specific effects in an inspiral flights close
to the event horizon of the black hole.
Software
The tool used in our work is the
Light++ raytracer,
which has its roots in the early 1990's.
It is a self-standing rendering engine and as such
free from any constraints imposed by standard
graphic libraries such as OpenGL.
In contrast to virtual reality languages, such as VRML or X3D,
which are used to visualize an explicitly
modeled object or the result of a simulation
performed elsewhere,
it allows to directly model a physical phenomena
and yields a visual result based on the implemented
laws of physics.
Here, the boundary among visualization and simulation
vanishes, as the visualization is a simulation
itself.
Acknowledgements
First of all we especially thank Yaakoub El Khamra for
his immense support on managing the rendering jobs on various
supercomputing resources and Shalini Venkataraman for
her involvement in frame postprocessing.
This research employed the resources of the Center for
Computation and Technology at Louisiana State University,
which is supported by funding from the Louisiana
legislature's Information Technology Initiative.
We thank Brian D. Ropers-Huilman for providing
fast and unbureaucratic support on administration issues
and computational time.
The camera path for the "black earth in the box" simulation
was provided by Marcel Ritter, University of Innsbruck, using
Maya.
Valuable suggestions, particularly on the topics of general
relativistic stereo viewing, are due to deep discussions
with Andrew Hamilton, University of Colorado, Boulder.
This work was partially supported by the National
Center for Supercomputer Applications under grant MCA02N014.
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