Progressive approaches offer a solution for time-critical applications.
They provide a result --- possibly sub-optimal --- whenever they are stopped and improve it with additional computing time.
Thus, a trade-off between the quality of the solution and computing time is achieved.
As the computing time of the visual hull is dependent on the number of contour points as well as on the number of outlines, we have developed a new method for refining a contour progressively. The proposed contour extraction method is deduced from the Marching-Squares-Algorithm, but allows to improve the results iteratively. In contrast to the Marching-Squares-Algorithm the new approach processes edges instead of cells and is called the Progressive-Edge-Algorithm. Starting from an initial coarse contour, the proposed method is able to improve whole images as well as selective parts of an image or of a contours.