Research And Implementation Of Hole Repair Algorithm In 3D Closed Triangle Mesh Model

With the vigorous development of emerging fields such as 3D printing,virtual reality,augmented reality,and digital cities,the 3D model has been increasingly spread and applied.The development and application of the tilt photography technology carried by drones has made it easier to quickly produce largest 3D models of existing real-world conditions,including scales as large as entire city.And many shared real-world modeling projects have appeared on the Internet.However,due to the possible dead angle in the image acquisition,or the matching cross section being too small,in the oblique photography process,the 3D real-world models are often built with holes.These holes need to be repaired to form a complete and watertight mesh model.Hole repair algorithm of 3D closed triangle mesh models has been studied in this dissertation.The main work is as follows:1.For holes in planar and curved regions in a non-closed triangular mesh model,the existing hole repair algorithm has been improved to handle island-shaped or multi-ring holes.The advancing-front mesh generation method(AFM)was used to ensure that the hole can always be patched and the normal of a new triangle always points to the outside of model in accordance with the original ones.Then,a method based on the Poisson deformation used to reshape the patch mesh for holes in curved regions was analyzed.This method ensures a smooth transition between the patch mesh and the around area and approximate the missing geometry more accurately.2.The problem of repairing missing holes in a 3D closed triangular mesh model was explored.A simple and effective hole repair method is proposed.Because there is a clear boundary between the triangular mesh of the hole area and those of the original model,the watershed algorithm is used to perform surface segmentation on the mesh first,and the quick convex hull algorithm is used to filter out the triangle mesh on the surface of the original model.Then,the question turns into repairing holes in the non-closed triangle mesh.For models with a large number of small islands,initial patch was generated using the AFM,starting from the largest part.And then the normal of new triangle is adjusted on the basis of the topological relationship between the various parts on the convex hull surface.Finally,a discrete Laplacian operator is used to smooth the mesh,keeping the topological structure of the new vertex unchanged,and adjusting the position of the new vertex to make the patch smoother.3.Using an open source 3D graphics processing library,a 3D model processing software module was developed to load and process the 3D scene model output from the upstream application.And the hole repair algorithm in the non-closed and 3D closed 3D mesh model was verified with samples in this software module.