A Blocking-based Triangulation of Surface Between Planar Contours

We proposed an approach to fit both global request and speed of recreation.That is,considering the fact that two adjacency cross-section contours of object are basically similar to each other,we first segment the area into several sections coarsely,and then triangulate within each section.What needs to be done first is detecting corner points.Many methods for corner detection have been proposed,such as corner detection based on multi-scale wavelet transformation,direction of edge chain code,CSS(curvature scale space) and polygon approximation about curvature,etc.Since some noises exist in curve,applied method about corner detection with de-noise ability is needed.We use common global optimization method.Here the advanced corner detection based on CSS is adopted.By using multi-scale processing,corner points are extracted from contours automatically.The second step is searching counterpart corner points from the two sets of corner dots.This step is to judge whether the two contours are similar with each other and to segment the space between them.For all similar contours,the quick triangulation algorithm introduced in this paper is applied.But for dissimilar contours,any global optimization method can be applied in the triangulation between them.We judge whether two corner dots in different contours are pairs based on the distance between them.A dynamic threshold is used and it depends on the distance between the planes in which the two contours lay and the curvatures at the dots.After the procession for corners,the similarity of contours should be confirmed.We think two contours to be similar if the number of corner pairs in them exceeds 70% that of corners in the contour with fewer corners on it.The final step is triangulation between two contours.For similar adjacency contours,we segment the space between them into smaller sections based on the matched corners.For each smaller section,any triangulation algorithms can be used but here we use a simple and quick method.During triangulating,the algorithm decides the next triangle on the basis of keeping the proportion of the numbers of the dots not used on two contours in accordance with that of total numbers.This algorithm distributed the task of triangulation between two adjacency contours into several smaller sections of them.Because of the corners' matching,a simple and quick triangulation could be used.Experiments show that the visual effect of our method is basically accord with that of normal global optimizing methods,but much less time is needed.So our method is effective.