In this paper we present a vision system that performs tracking a human face in 3D. To achieve this we combine color and stereo cues to find likely image regions where face may exist. A greedy search algorithm examines for a face candidate focusing the action around the position of the face which was detected in the previous time step. The aim of the search is to find the best-fit head ellipse....

Although local interactions involving orientation and spatial frequency are well understood, less is known about spatial interactions involving higher level pattern features. We examined interactive coding of aspect ratio, a prevalent two-dimensional feature. We measured perception of two simultaneously flashed ellipses by randomly post-cueing one of them and having observers indicate its aspec...

A novel ellipse fitting method which is selective for digital and noisy elliptic curves is proposed in this paper. The method aims at fitting an ellipse only when the data points are highly likely belong to an ellipse. This is achieved using the geometric distances of the ellipse from the data points. The proposed method models the non-linear problem of ellipse fitting as a combination of two o...

An ellipse rotating rigidly about its center may appear to rotate rigidly or to deform nonrigidly so that it appears gelatinous. We use this ambiguous stimulus to study how motion information is propagated across space. We find that features that are quite far from the contour of the ellipse may have a strong influence on the percept of the ellipse, provided they move in a way consistent with t...

A method for diagnosing the physical properties of a time-varying ellipse is presented. This essentially involves extending the notion of instantaneous frequency to the bivariate case. New complications, and possibilities, arise from the fact that there are several meaningful forms in which a time-varying ellipse may be represented. A perturbation analysis valid for the near-circular case clari...

An ellipse rotating rigidly about its center may appear to rotate rigidly or to deform nonrigidly so that it appears gelatinous. We use this ambiguous stimulus to study how motion information is propagated across space. We find that features that are quite far from the contour of the ellipse may have a strong influence on the percept of the ellipse, provided they move in a way consistent with t...

Participants explored ellipse perimeters defined by fixed-length strings, held taut by their moving finger, with ends attached to two fixed hooks (foci). Participants haptically judged ellipse interfocal distance (IFD; in effect, exocentric separation, or size at a distance) or location of ellipse major axes (i.e., egocentric localization relative to the moving finger). In Experiment 1A, percei...