Four-Sided Subdivision Algorithm of Curved Polygon

Aiming at the problems of model segmentation in the current volume parametric model construction,a four-sided subdivision algorithm of curved polygons based on the geometric features of curves is proposed.Firstly,contour curves,internal and external connection lines,contour polygons and other features are defined,and the feature inclusion tree is constructed by using the improved ray method.Then,starting from the leaf nodes at the leaf level of the feature inclusion tree,a series of subdomain subdivision operations are performed,including the acquisition and sorting of polygons in the domain with zero genus,search and sorting of the feasible subdivision lines,and the recursive quadrangle subdivision,so as to obtain the four-sided subdomain which is all convex.Finally,the Coons interpolation is carried out for all four-sided subdomains to generate NURBS surfaces,and the volume parametric model is obtained by stretching,scanning,rotation and loft operations.In the example part,five kinds of models with multi holes are selected and subdivided under the condition changes of the contours or the connection lines.The results show that the algorithm can quickly and accurately realize the four-sided subdivision for complex two-dimensional models with arbitrary genus.