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Perception, Virtual Environments, and Computer Graphics |
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Our research focuses on increasing the effectiveness of
computer graphics in conveying information about the three-dimensional
world. This is an interdisciplinary effort involving computer
graphics, perceptual psychology, and computational vision. We are
interested in better understanding the spatial information
potentially available in CG imagery, determining what spatial
cues are actually used when CG imagery is viewed, and using this
information to inform the development of improved rendering
algorithms.
Current projects: Perception of egocentric distance in visually
immersive environments. In visually immersive
environments such as HMDs, distance judgments to targets on
the ground are systematically compressed, at least for distances
in the range of 2m-20m. It is not clear why this is so.
The effect is apparent in a variety of response measures, suggesting
that it is the result of some sort of perceptual distortion. Visual
quality, binocular stereo, and the ability to see one's body do not
appear to have an influence on this phenomenon. The mass and moments of
an HMD do seem to cause a compression of space, at least as revealed
through blind walking to previously viewed targets, though not enough
to
account for what is seen in virtual environments. Current work is
exploring ways to compensate for HMD distance compression. Designing
Visually Accessible Spaces. The long-term goal of this
project is to provide tools to enable the design of safe environments
for the mobility of low-vision individuals and to enhance safety for
others, including the elderly, who may need to operate under low
luminance and other visually challenging conditions. One of the
main problems in designing for visual accessibility arises from the
difficulty of predicting the photometric appearance of real
spaces. The photograph of a child's block shows how lighting and
geometry can dominate reflectance in generating high and low contrast
visible edges. The bench is easily visible to many with low
vision under direct sunlight, but becomes a serious hazard under
lighting such as a cloudy day. This is a joint effort with the
University of Minnesota. Perceptual
coupling between perceived self motion and locomotion.
Humans calibrate their visually-directed actions to changing
circumstances in their environment. Both head-mounted displays (HMDs)
and well designed treadmill-based
virtual environments (treadmill-VE) can evoke a similar effect,
allowing the investigation of a number of open questions in
perception-action coupling that would be difficult or impossible to
investigate using real-world experimental apparatus. We have been able
to show a visual influence on both gait and "natural" walking speed and
have been able to probe questions such as whether the dominant visual
cue involved was based solely on 2-D optic flow or if instead a 3-D
reconstruction of the
speed of self motion was also involved. More recently, we have
explored how different categories of feedback affect subsequent actions
and more cognitive responses, both in the virtual world and in the real
world. Perceptual
aspects of locomotion
interfaces. Treadmills are an example of a locomotion
device allowing a user to walk in a relatively normal manner
without significant change in actual location. Our research deals with
combining more sophisticated locomotion devices with visual displays in
order to construct true locomotion interfaces which will allow
a user to interact with a virtual world by walking through that
world.A few not so current projects: Global
illumination as a cue for contact with a surface. Global
illumination cues can serve to visually "glue" objects to the
surfaces they are resting on, thereby avoiding the cookie cutter
appearance of simple computer graphics. While the use of shadows as
a contact cues has been known for some time, little research has yet
been done on the degree to which interreflections have a similar
effect. Almost nothing is currently known about how different CG
approximations to shadows and interreflections change the
perceptual effectiveness of these cues in conveying spatial
information.
Spatial processing of day-for-night images.
Conventional
day-for-night processing of images starts with daylight lit imagery and
simulates the appearance of night scenes by darkening the image,
reducing contrast, and introducing a blue shift. We have augmented this
processes to account for increased noise and reduced spatial acuity
at night. A key problem is to reduce acuity without introducing the
appearance of blur. (Click image for a larger view.)Faculty Sarah Creem-Regehr William B. Thompson Graduate Students Margarita Bratkova Benjamin Kunz Scott Kuhl Margaret Tarampi Tina Ziemek Alumni Valentina Dilda Amy A. Gooch Helen H. Hu Betty Mohler R. Keith Morley Cynthia Sahm Peter Shirley Peter Willemsen Leah Wouters Collaborators Claude Fennema, Jr. , Mount Holyoke College James Ferwerda , Cornell University Daniel Kersten , University of Minnesota Gordon Legge, University of Minnesota Herbert Pick, Jr. , University of Minnesota Erik Reinhard , University of Bristol John Rieser , Vanderbilt University Karen Sutherland , Augsburg College William Warren, Jr., Brown University Publications.. |
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