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178 Reverse Engineering – Recent Advances and Applications The block example (3in.×5in.×0.5in.) of 634,957 points shown in Fig. 4 is employed to illustrate the capabilities offered in Geomagic. As shown in Fig. 17a, primitive surfaces in most regions are recognized correctly. However, there are some regions incorrectly recognized; for example, the hole in the middle of the block was recognized as a free-form primitive, instead of a cylinder. There are also regions remained unrecognized; e.g., the middle slot surface. Fig. 17. Primitive surfaces recognized in Geomagic, (a) recognized regions, and (b) extracted primitive surfaces in SolidWorks Although most primitives are recognized in Geomagic, there are still issues to address. One of them is misrepresented profile. One example is that a straight line in a sketch profile may be recognized as a circular arc with a very large radius, as shown in Fig. 17b (this was found only after exporting the solid model to SolidWorks). The sketch profile will have to be carefully inspected to make necessary corrections, as well as adding dimensions and constraints to parameterize the profile. Unfortunately, such inspections cannot be carried out unless the solid model is exported to supported CAD systems. Lack of CAD-like capability severely restricts the usability of the solid models in Geomagic, let alone the insufficient ability for primitive surface recognition. 4.4.2 Rapidform XOR3 Rapidform offers much better capabilities than Geomagic for parametric solid modeling. Very good CAD-like capabilities, including feature tree, are available to the users. These capabilities allow users to create solid models and make design changes directly in Rapidform. For example, users will be able to create a sketch profile by intersecting a plane with the polygon mesh, and extrude the sketch profile to match the bounding polygon mesh for a solid feature. On the other hand, with the feature tree users can always roll back to previous entities and edit dimensions or redefine section profiles. These capabilities make Rapidform particularly suitable for parametric solid modeling. Rapidform offers two methods for solid modeling, Sketch, and Wizard, supporting fast and easy primitive recognition from segmented mesh. The major drawback of the Wizard is that some guide curves and profile
A Review on Shape Engineering and Design Parameterization in Reverse Engineering sketch generated are non-planar spline curves that cannot be parameterized. Users can use either or both methods to generate solid features for a single part. Method 1: Sketch In general, there are six steps employed in using the sketch method, (1) creating reference sketch plane, (2) extracting sketch profile by intersecting the sketch plane with the polygon mesh, (3) converting extracted geometric entities (usually as planar spline curves) into regular line entities, such as arcs and straight lines, (4) parameterizing the sketch by adding dimensions and constraints, (5) extruding, revolving, or lofting the sketches to create solid features; and (6) employing Boolean operations to union, subtract, or intersect features if necessary. Rapidform provides Auto Sketch capability that automatically converts extracted spline curves into lines, circles, arcs, and rectangles, with some constraints added. Most constraints and dimensions will have to be added interactively to fully parameterize the sketch profile. Steps 4 to 6 are similar to conventional CAD operations. With capabilities offered by Rapidform, fully constrained parametric solid models can be created efficiently. For the block example, a plane that is parallel to the top (or bottom) face of the base block was created first (by simply clicking more than three points on the surface). The plane is offset vertically to ensure a proper intersection between the sketch plane and the polygon mesh. The geometric entities obtained from the intersection are planar spline curves. The Auto Sketch capability of Rapidform can be used to extract a set of regular CAD-like line entities that best fit the spline curves. These standard line entities can be joined and parameterized by manually adding dimensions and constraints for a fully parameterized section profile, as shown in Fig. 18a. Fig. 18. A parametric solid model of the block example created using Rapidform, (a) fully parameterized section sketch, (b) extrusion for the base block, and (c) design change Once the sketch profile is parameterized, it can be extruded to generate an extrusion feature for the base block (Fig. 18b). The same steps can be followed to create more solid features, and Boolean operations can be employed to union, subtract, or intersect solid features for a fully parameterized solid model. The final solid model is analyzed by using Accuracy 179
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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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