figure 2. in the natural world, focus distance (the distance to which the eyes must focus to make an image sharp) and vergence distance (the distance at which the eyes’ lines of sight converge on an object) are the same. however, most stereoscopic 3D displays require viewers to point their eyes at simulated distances while still focusing on the display’s actual fixed distance. This incongruity can cause headaches and even nausea.

Real world
Stereo display

focal distance vergence distance

focal distance
vergence distance
display
surface

only will eliminate the need to wear special glasses, but also will have the ability to track head movement to render motion parallax accurately. And he predicts the proliferation of more powerful content-creation technologies, such as movie-production systems that can render a scene from different viewpoints without reshooting it, and an overall better understanding of vision fatigue related to focus and depth cues. With these and other technological advances, 3D viewing experiences will be greatly improved, whether they occur on big screens or small ones.

world. Banks is studying how the visual system can tolerate such slow updates and how viewers perceive such signals to be smooth and convincing.

“For these studies, it would be use-
ful to have faster display technology
than we currently have,” Banks says.
“With such technology, we would be
able to better understand the conse-
quences of using different temporal
protocols in the presentation of stereo-
scopic video.”
In a related project, Banks is study-
ing how blur affects the perception of
distance and size. Conventional opti-
cal devices, such as eyes and cameras,
can be focused only on one distance
at a time, which makes objects blurry
when they are farther from or nearer to
the focus distance. Banks is conduct-
ing studies to determine the relation-
ship between depth-of-field blur and
other depth cues, but also to under-
stand how changes in that relationship
affect human perception. The results
of such investigations could influence
the design of content for stereoscopic
3D cinema and television.

Further Reading

Akeley, K., Watt, S.J., Girshick, A.R., and Banks, M.S. A stereo display prototype with multiple focal distances. ACM Transactions on Graphics 23, 3, August 2004. Hoffman, D.M., Girshick, A.R., Akeley, K., and Banks, M.S. Vergence-accommodation conflicts hinder visual performance and cause visual fatigue. Journal of Vision 8, 3, March 28, 2008. Love, G.D., Hoffman, D.M., Hands, P.J. W., Gao, J., Kirby, A.K., and Banks, M.S. high-speed switchable lens enables the development of a volumetric stereoscopic display. Optics Express 17, 18, August 2009. Mendiburu, B. 3D Movie Making: Stereoscopic Digital Cinema from Script to Screen. Focal Press, Burlington, MA, 2009. Watt, S.J., Akeley, K., Ernst, M.O., and Banks, M.S. Focus cues affect perceived depth. Journal of Vision 5, 10, December 15, 2005.

based in los angeles, Kirk L. Kroeker is a freelance editor and writer specializing in science and technology.

Software

Automated Debugger for Parallel Programs

purdue university researchers, collaborating with high-performance computing experts at Lawrence Livermore national Laboratory, have created an automated debugging program for the simulations used to certify nuclear weapons.

called Automaded (for automata-based debugging for dissimilar parallel tasks), the program finds errors in com-

puter code for complex parallel programs.

International treaties forbid
the detonation of nuclear
test weapons, so certification
is performed with complex
simulations. these simulations
can last several weeks, and it
is common for an error in the
simulation code to not become
evident until long after it occurs,
which makes it difficult and
inefficient to locate the bug.

the primary developers of the program are Lawrence Livermore scientist greg Bronevetsky and purdue doctoral student Ignacio Laguna, and the paper, “Automaded: Automata-Based debugging for dissimilar parallel tasks,” was presented at the 40th Annual Ieee/IFIp International conference on dependable systems and networks in chicago.