We present here a discussion on the use of perceptual grouping to improve structure and egomotion recovery algorithms for monocular cameras. In particular we look at grouping lines to avoid the need for trinocular algorithms. We also present a number of methods for grouping lines, including a novel method that infers planar groups from those demonstrating a linear deformation.

Determining the motion of a camera from its image sequences has so far proved very difficult, and no practical algorithms have been found for freely moving cameras. This novel algorithm is based on motion parallax, but uses sparse visual motion estimates to extract the direction of translation of the camera directly, after which determination of the camera rotation and the depths of the image features follows easily. This method can also detect and reject independent motion, and provide a measure of the uncertainty of its estimates. 1