| OCR Text |
Show 83 right edge points are not really necessary for the X scan part of· the algorithm. It might be possible to dispense with the computation of the right silhouette edge trackers, however the right boundary edge trackers must be followed because they can turn into left edges if the Z component of their normal changes sign. Acceleratin onvergen Th@ average number of iterations necessary for convergence of the iteration points in a scene has proven to be roughly 2.5. This can be improved substantially by an extrapolation process on the position of the iteration points similar to that used in high order tracking algorithms. The u,v position of the iteration point on the previous Yscan value is saved along with the curren position. When updating to a new Yscan, the initial guess fed to the Newton iteration is computed, not as the current position, but as the position extrapolated from the previous two. This is illustrated in figure 22. V U"l. 2 u , - u" =- u Figure 22 - Extrapolation of Iteration Point Position Since the path of the iteration points in u,v is roughly |
