Event Location: NSH 1305
Bio: Li Zhang obtained his B.E. in Automation at Tsinghua University, P.R.
China, in 1998. He received his PhD from the Department of Computer
Science and Engineering at University of Washington in 2005. He worked
at Columbia University as a postdoctoral research scientist for two
years. He is now an assistant professor in the Department of Computer
Sciences at the University of Wisconsin-Madison. His research interests
include designing novel vision sensors, reconstructing and recognizing
3D shape and motion from images, animation, and display technologies.

Abstract: Traditional computer vision analyzes images taken under natural lighting
conditions, be they indoor or outdoor. With the advent of digital
projection technology, we can easily illuminate an environment with
programmed spatiotemporal lighting patterns. Such a lighting environment
provides new opportunities for computer vision research. I will overview
three recent projects that analyze images taken under this type of
lighting environment. First, I will present a temporal defocus method,
which reliably recovers the 3D structure of a scene, regardless of its
occlusion complexity. Then, I will present a spacetime stereo method
which accurately reconstructs objects that are deforming over time. Both
methods significantly outperform the state-of-the-art techniques for 3D
sensing. I will demonstrate several applications of the proposed methods
to computer graphics, including image refocusing, video composition,
expression synthesis, and facial animation. Finally, I present a method
of using projected light to create optical (“virtual”) tags in a scene.
Each tag carries information about its own 3D location and the identity
of the object it falls on. Such a tagging method enables us to detect
and recognize not only objects that visible in an image but also the
ones that are occluded or slightly outside the field-of-view of the image.