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172 Reverse Engineering – Recent Advances and Applications One important finding worth noting is that the mesh segmentation capability is only available in Geomagic and Rapidform. This capability allows users to adjust a sensitivity index to vary the size of segmented regions so that the regions match closely to the distinct surfaces of the object. Such segmentation is critical since the properly segmented regions facilitate surface fitting and primitive feature recognition. Based on the findings, we exclude further discussion on SolidWorks and Wildfire due to their poor performance in the first evaluation round. In the following we discuss results of Geomagic and Rapidform for selected examples to consolidate our conclusions. 4.3.1 Geomagic Studio v.11 Geomagic demonstrates an excellent surface construction capability with a high level of automation. Based on our evaluations, excellent NURB surface models can be created for all five examples from their respective scanned data in less than 30 minutes. In addition, Geomagic offers interactive capabilities that allow users to manually edit or create geometric entities. For examples, Point Phase of Geomagic supports users to edit points, reduce data noise, and adjust sampling to reduce number of point data. After point editing operations, polygon meshes are created by using Wrap. In Mesh Phase, self-intersecting, highly creased edges (edge with sharp angle between the normal vectors of the two neighboring polygonal faces), spikes and small clusters of polygons (a group of small isolated polygon meshes) can be detected and repaired automatically by Mesh Doctor. Mesh editing tools; such as smooth polygon mesh, define sharp edges, defeature and fill holes; are also provided to support users to create quality polygon meshes conveniently. Once a quality mesh is generated, Shape Phase is employed to create NURB surfaces best fit to the polygon mesh. Auto Surface consists of a set of steps that automatically construct surface models. The steps include Detect Contour, Construct Patches, Construct Grids and Fit Surfaces. Before using Auto Surface, users only have to consider the quality of the surface model (for example, specifying required tolerance) and the method (for example, with or without mesh segmentation). For the block example, we set surface tolerance to 0.01 inch and construct NURB surface model with Detect Contours option (which performs mesh segmentation) using Auto Surface. A complete NURB surface model was created in 5 minutes (Fig. 8). Average deviation of the NURB model is 0.0 inch and the standard deviation is 0.0003 inch. The deviation is defined as the shortest distance (a signed distance) between the polygon mesh and the NURB surfaces. Note that in Figure 8d, green area indicates deviation close to 0 and red spot indicates the max deviation, which is about 0.017 inch in this case. Fig. 8. Results of the block example tested using Geomagic, (a) point cloud model (634,957 points), (b) polygon mesh (1,271,924 triangles), (c) NURB surface model, and (d) deviation analysis
A Review on Shape Engineering and Design Parameterization in Reverse Engineering Two more examples, tubing and sheetmetal, are processed following the same steps. Results are shown in Figs. 9 and 10, respectively. These examples demonstrate that Auto surface of Geomagic offers reliable, viable and extremely efficient capability for automated surface reconstruction. Fig. 9. Results of the tubing example tested using Geomagic, (a) polygon mesh (589,693 triangles), (b) NURB model (1,107 patches), and (c) deviation analysis Fig. 10. Results of the sheet metal example tested using Geomagic, (a) polygon mesh (126,492 triangles), (b) NURB model (91 patches), and (c) deviation analysis 4.3.2 Rapidform XOR3 Like Geomagic, Rapidform offers excellent capabilities for point data editing and polygon mesh generation, including data sampling, noise reduction, wrap, mesh repair, defeature, and fill holes. Auto Surfacing for NURB surface construction in Rapidform contains two methods, (1) Feature Following Network (with mesh segmentation), and (2) Evenly Distribution Network (without mesh segmentation). Feature Following Network is a very good option for surface reconstruction in XOR3. Segmentation was introduced into Auto Surfacing to overcome problems of surface transition across sharp edges, especially dealing with mechanical parts with regular features. Using Feature Following Network sharp edges can be detected and retained in the surface model. Feature Following Network is usually more successful in surface construction. For example, in Fig. 11a, several gaps (circled in red) are found in the block example, mostly along narrow and high curvature transition regions, while using Evenly Distribution Network option for constructing surfaces. Using Feature Following Network option the surface model constructed is air-tight with sharp edges well preserved, as shown in Fig. 11b. Note that large size NURB surfaces (therefore, less number of NURB surfaces) shown in Fig. 11b tend to be created due to incorporation of mesh segmentation. The NURB surface model of the block example (Fig. 12a) was successfully created using Feature Following Network option in just about 5 minutes (Fig. 12b). The accuracy measures; i.e., the deviation between the surface model and the polygon mesh, are 0.00 inch and 0.0006 inch in average and standard deviation, respectively, as shown in Fig. 12c. 173
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REVERSE ENGINEERING - RECENT ADVANC
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Contents Preface IX Part 1 Software
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Preface Introduction In the recent
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Preface XI and con’s related to t
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Preface XIII the step-by-step appli
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Part 1 Software Reverse Engineering
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4 Reverse Engineering - Recent Adva
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10 Reverse Engineering - Recent Adv
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58 2. Model driven architecture: An
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62 Fig. 1. Model, metamodels and tr
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100 Reverse Engineering - Recent Ad
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108 Table 1. Number of smoothers an
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1. Introduction 60 Surface Reconstr
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Surface Reconstruction from Unorgan
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238 5. Summary and discussions Reve
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268 Fig. 6. A closed polygon mesh r
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272 3. Results Reverse Engineering
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