**5. Discussion**

182 Reverse Engineering – Recent Advances and Applications

The *block* example that was fully parameterized in *Rapidform* was first exported to *SolidWorks*. All the solid features were seamlessly exported to *SolidWorks*, except for some datum entities, such as datum points. Since entities such as polygon meshes and segmented regions are not included in *SolidWorks* database, they cannot be exported. As a result, geometric datum features associated with these entities are not exported properly. The dimensions and constraints added to the sketches and solid features in *Rapidform* are exported well, except again for those referenced to entities that are not available in *SolidWorks*. Fortunately, it only requires users to make a few minor changes (such as adding or modifying dimensions or constraints) to bring back a fully parametric solid model in *SolidWorks*. As shown in Fig. 22, the length of the base block was increased and the solid model is rebuilt in *SolidWorks* (Fig. 22b). Similar results were observed in *NX*. However,

Fig. 21. The *block* model explored to *SolidWorks* and *Wildfire*, (a) seventeen features

*Wildfire* 

and (b) design change made in *SolidWorks* 

recognized in *Geomagic*, (b) features exported to *SolidWorks* (wireframe), (c) features "piled up" in *SolidWorks*, (d) features exported to *Wildfire* (wireframe), and (e) features "piled up" in

Fig. 22. *Block* exported from *Rapidform* to *SolidWorks*, (a) solid model exported to *SolidWorks*,

The most useful and advanced shape engineering capabilities are offered in specialized, non-CAD software, such as *Geomagic*, *Rapidform*, etc., that are intended to support reverse engineering. Some CAD packages, such as *SolidWorks*, *Pro/ENGINEER Wildfire*, and *CATIA*, offer limited capabilities for shape engineering. In general, capabilities offered in CAD are labor intensive and inferior to specialized codes while dealing with shape engineering.

After intensive review and survey (Chang & Chen, 2010), to the authors' knowledge, the best software on the market for reverse engineering is *Geomagic Studio* v.11 and *Rapidform XOR3*. This was determined after a thorough and intensive study, following a set of prescribed criteria including auto surfacing, parametric solid modeling, and software usability. Between the two, *Geomagic* has a slight edge in geometric entity editing, which is critical for auto surfacing. In terms of solid modeling, *Geomagic* stops short at only offering primitive surfaces, such as plane, cylinder, sphere, etc., from segmented regions.

*Rapidform* is superior in support of solid modeling (in addition to excellent auto surfacing) that goes beyond primitive surface fitting. *Rapidform* offers convenient sketching capabilities that support feature-based modeling. As a result, it often requires less effort yet yielding a much better solid model by interactively recovering solid features embedded in the segmented regions. The interactive approach mainly involves creating or extracting section profiles or guide curves from the polygon mesh, and following CAD-like steps to create solid features.
