3D Motion Segmentation Using Intensity Trajectory

Motion segmentation is a fundamental aspect of tracking in a scene with multiple moving objects. In this paper we present a novel approach to clustering individual image pixels associated with different 3D rigid motions. The basic idea is that the change of the intensity of a pixel can be locally approximated as a linear function of the motion of the corresponding imaged surface. To achieve appearance-based 3D motion segmentation we capture a sequence of local image samples at nearby poses, and assign for each pixel a vector that represents the intensity changes for that pixel over the sequence. We call this vector of intensity changes a pixel “intensity trajectory”. Similar to 2D feature trajectories, the intensity trajectories of pixels corresponding to the same motion span a local linear subspace. Thus the problem of motion segmentation can be cast as that of clustering local subspaces. We have tested this novel approach using some real image sequences. We present results that demonstrate the expected segmentation, even in some challenging cases.