p094fig03.07 The processes of boundary completion and surface filling-in are computationally complementary.<BR>||  <TABLE border="1"><TR><TD><B>Boundary completion</td><TD><B>Surface filling-in</td></tr><TR><TD>outward</td><TD>inward</td></tr><TR><TD>oriented</td><TD>unoriented</td></tr><TR><TD>insensitive to direction of contrast</b></td><TD>sensitive to direction-of-contrast</td></tr></table>