Perception & Action Lab

3D Perception

In a short treatise on visual perception, Ernst Mach wrote that, "we do not see optical images in an optical space, but we perceive the bodies round about us in their many and sensuous qualities." To put it in more modern parlance, "A central puzzle in vision is how the brain infers properties of the world ('bodies round about us') from uncertain and ambiguous sensory data ('optical images in an optical space').

We use computational modeling to study, in theory, the nature of the visual information available in images about the 3-D shapes and orientations of surfaces in a scene, We use human psychophysics to decompose the computations used by the brain to perceive the world in 3-D. In our psychophysical studies, we use virtual reality displays to manipulate the visual information available to an observer and to measure their 3-D percepts. Projects in the lab have focused on a number of problems, including the perception of 3-D object motion from the motion of cast shadows, the perception of surface shape from contours, the perception of surface shape from texture and the perception of shape from shading. A major current focus of the lab is how the visual system integrates the information from different visual cues to generate a unified percept of 3D surface orientation and shape.

Landy, M. S., Banks, M. and Knill, D. C. (2011) Ideal-Observer Models of Cue Integration, in (Trommershauser, J. Kording, K., and Landy, M. S. eds.) Sensory Cue Integration, Osford Univ. Press, Oxford, England.
Seydell, A., Knill, D. C. and Trommershauser, J. (2011) Priors and Learning in Cue Integration, in (Trommershauser, J. Kording, K., and Landy, M. S. eds.) Sensory Cue Integration, Osford Univ. Press, Oxford, England.
Seydell, A., Knill, D. C. and Trommershauser, J. (2010) Adapting internal statistical models for interpreting visual cues to depth, Journal of Vision. 10 (4), Article 1. PDF
Greenwald, H. and Knill, D. C. (2009) Cue Integration Outside Central Fixation: A Study of Grasping in Depth, Journal of Vision, Vol. 9, No. 2, 1 - 16. PDF
Greenwald, H. and Knill, D. C. (2009) Orientation Disparity: A Cue for 3D Orientation, Neural Computation, Vol. 21, No. 9, Pages 2581-2604. PDF
Knill, D. C. (2007) Robust cue integration: a Bayesian model and evidence from psychophysical studies with stereoscopic and figure cues to slant, Journal of Vision, 7 (7), 1 – 24. PDF
Knill, D. C. (2007) Learning Bayesian priors for depth perception, Journal of Vision, 7 (8), 1 – 20. PDF
Knill, D. C. (2007) Bayesian models of sensory cue integration, in (Doya, K., Ishii, S., Pouget, A. and Rao, R., eds.) Bayesian Brain: Probabilistic Approaches to Neural Coding, MIT Press, Cambridge, MA. PDF
Atkins, J. E., Jacobs, R. A. and Knill, D. C. (2003) Experience-Dependent Visual Cue Recalibration Based on Discrepancies Between Visual and Haptic Percepts, Vision Research., 43 (25): 2603-2613. PDF
Knill, D. C. and Saunders, J. (2003) Do humans optimally integrate stereo and texture information for judgments of surface slant? Vision Research, 43 (24), 2539-58. PDF
Knill, D. C. (2003) Mixture models and the probabilistic structure of depth cues, Vision Research, 43 (7), 831-854. PDF
Saunders, J. and Knill, D. C. (2001) Perception of 3D surface orientation from skew symmetry, Vision Research, 41 (24), 3163 - 3185. PDF
Sen, M. G., Yonas, A., and Knill, D. C. (2001). Development of infants' sensitivity to surface contour information for spatial layout, Perception, 30 (2), 167-176. PDF
Knill, D. C. (2001) Contour into texture: The information content of surface contours and texture flow, Journal of the Optical Society A, 18 (1), 12-36. PDF
Mamassian, P., Knill, D. C. and Kersten, D. (1998) Perceiving spatial layout from cast shadows, Trends in Cognitive Science, 2 (8), 288-295. PDF
Knill, D. C. (1998) Surface orientation from texture: Ideal observers, generic observers and the information content of texture cues, Vision Research, 38 (11), 1655-1682. PDF
Knill, D. C. (1998) Discriminating planar surface slant from texture: Human and ideal observers compared, Vision Research, 38 (11), 1683-1711. PDF
Knill, D. C. (1998) Ideal observer perturbation analysis reveals human strategies for inferring surface orientation from texture, Vision Research, 38 (17): 2635-2656. PDF
Knill, D. C., Mamassian, P. and Kersten, D. (1997) The geometry of shadows, Journal of the Optical Society of America, 14 (12), 3216-3232. PDF
Kersten, D., Mamassian, P. and Knill, D. C. (1997) Moving cast shadows induce apparent motion in depth, Perception, 26 (2), 171-192. PDF
Kersten, D., Knill, D.C., Mamassian, P. and Bulthoff, I. (1996) Illusory motion from shadows, Nature 379 (6560), 31. PDF
Mamassian, P., Kersten, D. & Knill, D. C. (1996), Categorical local shape perception, Perception, 25, 95-107. PDF
Liu, Z., Knill, D. C., & Kersten, D. (1995), Object classification for human and ideal observers, Vision Research 35 (4), 549-569. PDF
Knill, D. C., Mamassian, P. and Kersten, D. (1993) The geometry of shadows, University of Minnesota Computer Science Technical Report, TR 93-47.
Yonas, A., Knill, D. C., Sen, A. and Bittinger, K. A. (1993) The development in human infants of sensitivity to surface contour information for 3-D layout, in (Valenti, S. S. and Pittenger, J., eds.)Studies in Perception and Action II, Lawrence Erlbaum Associates Publishers, Hillsdale, New Jersey.
Yonas, A., Sen, A. and Knill, D. C. (1993) Reconceptualizing accretion and deletion of texture, to appear in (Valenti, S. S. and Pittenger, J., eds.)Studies in Perception and Action II, Lawrence Erlbaum Associates Publishers, Hillsdale, New Jersey.
Knill, D. C. (1992) The perception of surface contours and surface shape: from computation to psychophysics. Journal of the Optical Society of America A., 9 (9), 1449-1464. PDF
Knill, D. C. & Kersten, D. (1991) Apparent surface curvature affects lightness perception. Nature, 351, 228-230. PDF
Knill, D. C. & Kersten, D. (1990) Learning a near-optimal estimator for surface shape from shading. Computer Vision, Graphics and Image Processing, 50, 75-100.
Knill, D. C. (1990) Estimating illuminant direction and degree of surface relief. Journal of the Optical Society of America A, 7 (4), 759-775. PDF