Copyright © 2018 Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. International Journal of Engineering & Technology, 7 (2.15) (2018) 81-85 International Journal of Engineering & Technology Website: www.sciencepubco.com/index.php/IJET Research Paper Filling Simple Holes of Triangular Mesh by using Enhanced Advancing Front Mesh (EAFM) method Noorehan Awang 1,2 , Rahmita Wirza Rahmat 1 *, Puteri Suhaiza Sulaiman 1 , Azmi Jaafar 1 , Ng Seng Beng 1 1 Faculty of Computer Science and Information Technology, Universiti Putra Malaysia, Serdang, Selangor. 2 Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA, Malaysia. *Corresponding author E-mail: rahmita@fsktm.upm.edu.my Abstract Triangular meshes are extensively used to represent 3D models. Some surfaces cannot be digitised due to various reasons such as inade- quacy of the scanner, and this generally occurs for glossy, hollow surfaces and dark-coloured surfaces. This cause triangular meshes to contain holes and it becomes difficult for numerous successive operations such as model prototyping, model rebuilding, and finite ele- ment analysis. Hence, it is necessary to fill these holes in a practical manner. In this paper, the Enhanced Advancing Front Mesh (EAFM) method was introduced for recovering missing simple holes in an object. The first step in this research was to extract the feature vertices around a hole on a 3D test data function. Then the Advancing Front Mesh (AFM) method was used to fill the holes. When conflicts oc- curred during construction of the triangle, the EAFM method was introduced to enhance the method. The results of the study show that the enhanced method is simple, efficient and suitable for dealing with simple hole problems. Keywords: Triangular, Hollow, Holes, Mesh, Surfaces 1. Introduction The reverse engineering model transforms the current physical or product model into a conceptual or engineering design prototype. With the development and application of computer technology; especially the theories and techniques of computer aided geomet- ric design, reverse engineering has become an important means to obtain three dimensional models. Reverse engineering includes data acquisition, data processing and surface reconstruction, which have become key technologies in reverse engineering[1,2]. There are two model types of surface reconstruction, namely discrete grid and parametric surface. For the discrete grid model, the defi- nition of triangular mesh is relatively simple. The ability descrip- tion of the complex topology is strong, and related algorithms are more mature; thus, triangular mesh has become the more common model representation. The triangular mesh can be considered as the most sought after output of surface reconstruction, as the primary issue of surface reconstruction is to depict the topology. The triangular mesh can successfully represent the topology in a simple and efficient man- ner. However, if more elaborate representation is required, more properties are needed. The triangular mesh data can be derived through different ways such as optical flow, 3 dimensional (3D) scanner, and computer-aided design software. Data points can be categorised as structured (dense) or unstructured (scattered) data points. The research focused on the data obtained from a 3D scan- ner; predominantly as scattered data points [3]. The scattered data points are the points that have no structure or order between their relative locations. There are three key sources of scattered data: computational values, measured values of physi- cal quantities and experimental results [4]. However, due to the limitations of the scanner, some surfaces cannot be digitised, usu- ally for dark-coloured, glossy or hollow surfaces. Hence, the con- sequent triangular mesh models cannot be used directly by other applications, mostly due to their incomplete structure, that is, the presence of defects such as holes, gaps, self-intersecting triangles, etc. in the structure [5]. There are two key kinds of holes, classified as ring holes and sim- ple holes. This research emphasises on a simple hole, i.e. a hole of any shape with just one boundary loop [6]. Simple holes have no feature vertices except those who share common boundary verti- ces with other holes [7]. Simple holes can be filled with planar triangulations which are executable when all boundary edges can be projected into a plane, without self-intersection [8,9]. Latest research on filling simple holes was discovered by many researcher [10-14]. Several researchers also have conducted a great deal of research on AFM. One of the study introduced AFM technique to fill simple and complex holes. Next, the normal vec- tor of each triangle was used to solve a Poisson equation accord- ing to the normal vector and hole-boundary points, which then adjusted the position of the new points. However, when there were too many points, the Poisson equation solution would be too time- consuming [15]. In another research, triangulated holes using the improved AFM method and a series of initial patch meshes over the holes, were obtained and a weighted bi-umbrella operator was used to optimize the initial patch. The main constraint of this algo- rithm is that the filling result may lose some geometric details for holes that are too big [16]. A study by one researcher use Genetic Algorithm to obtain a valid and optimal initial triangulation then a customized Advancing Front meshing was performed over the approximated holes to generate an unstructured triangular mesh over the region [6]. A