Optical Snow

摘要

Classical methods for measuring image motion by computer have concentrated on the cases of optical flow in which the motion field is continuous, or layered motion in which the motion field is piecewise continuous. Here we introduce a third natural category which we call optical snow. Optical snow arises in many natural situations such as camera motion in a highly cluttered 3-D scene, or a passive observer watching a snowfall. Optical snow yields dense motion parallax with depth discontinuities occurring near all image points. As such, constraints on smoothness or even smoothness in layers do not apply. In the Fourier domain, optical snow yields a one-parameter family of planes which we call a bowtie. We present a method for measuring the parameters of the direction and range of speeds of the motion for the special case of parallel optical snow. We demonstrate the effectiveness of the method for both synthetic and real image sequences.