| OCR Text |
Show 79 iteration points are added to the active list, necessary to update the positions of all points to their it is correct values on the new scan plane. This simply involves calling on the bivriate iteration procedure for the silhouette trackers and the univariate iteration for all boundary trackers. Each of these could fail either because the ,point iterated outside 2 boundary or because it got caught at a local minimum of the Y function. Points should fail due to the latter case in pairs in which case they should be deleted from the list. Points failing because of iterating across 2 _ patch boundary also should be removed. Boundary edge trackers which iterate across another boundary (at a corner of the patch), should, however, be examined further. Before deleting the point, an attempt should be made to see if the Y=Yscan condition can be satisfied on the boundary it tried to cross. If so, the point is left active and it then continues to track the new boundary. The point has, so to speak, turned the corner. In this way, separate mechanism for creating new iteration points at each corner is unnecessary. The X Scan - ---- The X scan is responsible for maintaining the list of active intersection points 2S the scan ray sweeps from left to right across the picture. Intersection points are those formed by the intersection of the X scan ray with the cross section curve in XZ. Points enter and exit at boundary |
