Stereoscopic Visualization of Curved Space

The Light group: Werner Benger, Brad Corso, Erin Gillilan, Manuel Tiglio

Left eye image
Right eye image
Monoscopic mpeg:
[732x480]     [1900x1080]

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
Right eye image
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.