University of Utah Perception and Computer Graphics Research Group

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

wooden block with surfaces of 80% and 20% albedo plus bench that
is difficult to see in diffuse lighting

wooden block with surfaces of 80% and 20% albedo plus bench that
is difficult to see in diffuse lighting

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.

hallway scene

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.

Treadport

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

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
     Rose Mills (Cipriano)
     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..