**4. Engineering software evaluations**

The key criteria for the software evaluations are the capabilities of supporting automatic surface construction from point clouds and parametric solid modeling. We did the first screening on nine leading software tools that are commercially available. This screening was carried out based on the information provided in product brochure, technical reports (for example, Siddique, 2002; Chang et al., 2006), thesis (for examle, Gibson, 2004), company web sites, on-line software demo, case study reports, etc. After the screening, we acquired four tools and conducted hands-on evaluations, using five industrial examples. With this, we are able to identify pros and cons in each software tool, make a few observations, and conclude the study.

## **4.1 Software screening**

After extensive research and development in the past decade, software tools for reverse engineering have made impressive advancement. In general, these tools can be categorized into two groups, feature-based and RE-based. The feature-based CAD packages, such as *Pro/ENGINEER*, *SolidWorks*, and *CATIA*, emphasize recovering the original design intents of the parts. Following standard CAD capabilities, such as sketching, extrusion, and Boolean operations, designers are able to create parts with design intents recovered. On the contrary, RE-based packages; such as *Geomagic*, *Rapidform*, and *Paraform*, focus on reconstructing the geometry of the objects from scanned data, usually in the form of NURB surfaces. RE-based packages offer excellent capabilities in editing points, creating meshes, and generating NURB surfaces. In addition, the display performance of mass data offered by the RE-based package is far better than the feature-based CAD software; that is, in the context of reverse engineering.

In this study, we looked for two key engineering capabilities; i.e., surface construction and parametric solid modeling from a point cloud or a polygon mesh. All feature-based and REbased software tools offer some capabilities for surface constructions. However, manually constructing curves and surfaces from point clouds or polygon meshes are tedious and extremely time consuming. It is critical that a serious RE software must offer auto surfacing; i.e., allowing for creating air-tight, high accuracy, and high quality surface models with only a few button clicks. On the other hand, constructing solid models has to be carried out in an interactive manner, allowing designers to recover original design intents. Software must offer adequate capabilities to assist designers to sketch section profiles and create solid features efficiently, without directly dealing with point clouds or polygon meshes. Certainly, the software will have to be stable and capable of handling massive data. Millions of point data need huge computer resources to process. Zoom, pan or rotate the object, for example, on the screen may take time for software to respond. Speed is the key for modern RE-based software. We are essentially searching for software that offers auto surfacing and parametric modeling capabilities with fast and stable performance.

In addition, several software related criteria are defined, as listed in Table 1. These criteria are categorized into four groups, (1) general capabilities, such as speed; (2) generation of NURB models, including auto surfacing and geometric entity editing capabilities; (3) generation of solid models, including section profiling and parametric capabilities; and (4) usability.

From Table 1, we observe that most surveyed software offers basic capabilities for editing and manipulating points, polygon meshes and NURB curves and surfaces. Particularly, we found both *Geomagic* and *Rapidform* support auto surfacing. Solid modeling using scanned 168 Reverse Engineering – Recent Advances and Applications

The key criteria for the software evaluations are the capabilities of supporting automatic surface construction from point clouds and parametric solid modeling. We did the first screening on nine leading software tools that are commercially available. This screening was carried out based on the information provided in product brochure, technical reports (for example, Siddique, 2002; Chang et al., 2006), thesis (for examle, Gibson, 2004), company web sites, on-line software demo, case study reports, etc. After the screening, we acquired four tools and conducted hands-on evaluations, using five industrial examples. With this, we are able to identify pros and cons in each software tool, make a few observations, and conclude

After extensive research and development in the past decade, software tools for reverse engineering have made impressive advancement. In general, these tools can be categorized into two groups, feature-based and RE-based. The feature-based CAD packages, such as *Pro/ENGINEER*, *SolidWorks*, and *CATIA*, emphasize recovering the original design intents of the parts. Following standard CAD capabilities, such as sketching, extrusion, and Boolean operations, designers are able to create parts with design intents recovered. On the contrary, RE-based packages; such as *Geomagic*, *Rapidform*, and *Paraform*, focus on reconstructing the geometry of the objects from scanned data, usually in the form of NURB surfaces. RE-based packages offer excellent capabilities in editing points, creating meshes, and generating NURB surfaces. In addition, the display performance of mass data offered by the RE-based package is far better than the feature-based CAD software; that is, in the context of reverse engineering. In this study, we looked for two key engineering capabilities; i.e., surface construction and parametric solid modeling from a point cloud or a polygon mesh. All feature-based and REbased software tools offer some capabilities for surface constructions. However, manually constructing curves and surfaces from point clouds or polygon meshes are tedious and extremely time consuming. It is critical that a serious RE software must offer auto surfacing; i.e., allowing for creating air-tight, high accuracy, and high quality surface models with only a few button clicks. On the other hand, constructing solid models has to be carried out in an interactive manner, allowing designers to recover original design intents. Software must offer adequate capabilities to assist designers to sketch section profiles and create solid features efficiently, without directly dealing with point clouds or polygon meshes. Certainly, the software will have to be stable and capable of handling massive data. Millions of point data need huge computer resources to process. Zoom, pan or rotate the object, for example, on the screen may take time for software to respond. Speed is the key for modern RE-based software. We are essentially searching for software that offers auto surfacing and

parametric modeling capabilities with fast and stable performance.

In addition, several software related criteria are defined, as listed in Table 1. These criteria are categorized into four groups, (1) general capabilities, such as speed; (2) generation of NURB models, including auto surfacing and geometric entity editing capabilities; (3) generation of

From Table 1, we observe that most surveyed software offers basic capabilities for editing and manipulating points, polygon meshes and NURB curves and surfaces. Particularly, we found both *Geomagic* and *Rapidform* support auto surfacing. Solid modeling using scanned

solid models, including section profiling and parametric capabilities; and (4) usability.

**4. Engineering software evaluations** 

the study.

**4.1 Software screening** 

data can be commonly achieved by creating section sketches from polygon meshes and following feature creating steps similar to CAD packages. Based on the survey, *Rapidform* is found the only software that supports parametric solid modeling. For hands-on evaluations, we selected *Geomagic* and *Rapidform*, in addition to a few CAD packages.


Table 1. A summary of commercial software tools surveyed

A Review on Shape Engineering and Design Parameterization in Reverse Engineering 171

Based on the evaluations, we found that all software tools evaluated are able to support surface modeling either fully automatically or close to fully automation. Table 4 summarizes the test results. The results show that *Geomagic* is the only software that is able to create surface models for all five examples automatically, without any user interventions. *Rapidform* comes close second. *Rapidform* is able to construct surface models for two out of the five examples fully automatically. For the remaining three examples, only minor interventions or editing from the user are required. However, *SolidWorks* and *Wildfire* are able to support only some of the examples even after spending long hours. It took extremely long time using *SolidWorks* or *Wildfire* to process some of the examples, and yet without achieving meaningful results. Software crashed without giving warning message while conducting triangulation or surface fitting. The size of the scanned data also presents problems for *SolidWorks* and *Wildfire*. They are able to support only up to about 300,000 data points. The software becomes unstable or even crashes while handling more data points.

> Model 3 *Sheetmetal*

Completed (Automated)

Completed (Partial-auto)

Fail (Gaps remained, shown in red)

Completed (Automated) Model 4 *Blade* 

Completed

Completed

Completed

Completed

(Automated) Completed

(Partial-auto) Completed

(Automated) Software

(Automated) Software

Model 5 *Door Lock* 

(Automated)

(Automated)

crashed

crashed

Model 1 *Block* 

Completed (Automated)

Completed (Automated)

Fail (Gaps remained, shown in red)

> Software Crashed

Table 4. Results of Round 1 evaluations

Geomagic Studio v.11

Rapidform XOR3

SolidWorks 2009

> Wildfire v.4

Model 2 *Tubing* 

Completed (Automated)

Completed (Partial-auto)

> Software crashed

> Software crashed

## **4.2 Examples for hands-on evaluations**

For hands-on evaluations, we carried out two rounds of study; round 1 focuses on auto surfacing, and round 2 is for parametric solid modeling. After surveying most advanced software as discussed in Section 4.1, we selected four candidate software tools for hands-on evaluations. They are RE-based software *Geomagic Studio v.11* and *Rapidform XOR3*; and feature-based CAD software *Pro/ENGINEER Wildfire v.4* and *SolidWorks 2009*. As shown in Table 2, all tools support surface and solid model construction, except for *Wildfire*, which does not support parametric solid modeling using scanned data.


Table 2. Software selected for hands-on evaluations

For round 1 evaluations, we focus on auto surfacing and the software stability. In round 2, we focus on parametric solid modeling, we look for primitive feature recognition (such as cylinder, cone, etc.), parametric modeling, and model exporting to CAD packages.

We selected five examples for hands-on evaluation, as listed in Table 3. Among the five examples, two are given as polygon meshes and the other three are point clouds. These five parts represent a broad range of applications. Parts like the *block*, *tubing*, and *door lock* are more traditional mechanical parts with regular solid features. In contrast, *sheetmetal* part (Model 3) is a formed part with large curvature, and the *blade* is basically a free-form object.


Table 3. Examples selected for hands-on evaluations

#### **4.3 Round 1: Auto surfacing**

In round 1 evaluation, we are interested in investigating if software tools evaluated are able to support auto surfacing; i.e., automatically constructing air-tight, accurate, and high quality surface models from scanned data. We look for the level of automation, software stability, and capabilities for editing geometric entities (such as points, meshes, and NURB patches).

170 Reverse Engineering – Recent Advances and Applications

For hands-on evaluations, we carried out two rounds of study; round 1 focuses on auto surfacing, and round 2 is for parametric solid modeling. After surveying most advanced software as discussed in Section 4.1, we selected four candidate software tools for hands-on evaluations. They are RE-based software *Geomagic Studio v.11* and *Rapidform XOR3*; and feature-based CAD software *Pro/ENGINEER Wildfire v.4* and *SolidWorks 2009*. As shown in Table 2, all tools support surface and solid model construction, except for *Wildfire*, which

For round 1 evaluations, we focus on auto surfacing and the software stability. In round 2, we focus on parametric solid modeling, we look for primitive feature recognition (such as

Rapidform XOR3 Auto Surfacing Solid/ Surface Primitives

Geomagic Studio v. 11 Shape Phase Fashion Phase

SolidWorks 2009 Scan to 3D Scan to 3D Wildfire v. 4 Facet + Restyle Not Available

We selected five examples for hands-on evaluation, as listed in Table 3. Among the five examples, two are given as polygon meshes and the other three are point clouds. These five parts represent a broad range of applications. Parts like the *block*, *tubing*, and *door lock* are more traditional mechanical parts with regular solid features. In contrast, *sheetmetal* part (Model 3) is a formed part with large curvature, and the *blade* is basically a free-form object.

> Model 3 *Sheetmetal*

Surface Reconstruction Parametric Modeling

134,089 polygons

16×10×9 (inch)

Model 4 *Blade* 

252,895

2×3×4 (inch)

Model 5 *Door Lock* 

> 7×3×2 (inch)

points 207,282 points

cylinder, cone, etc.), parametric modeling, and model exporting to CAD packages.

Model 2 *Tubing* 

polygons

125×93×17 (mm)

In round 1 evaluation, we are interested in investigating if software tools evaluated are able to support auto surfacing; i.e., automatically constructing air-tight, accurate, and high quality surface models from scanned data. We look for the level of automation, software stability, and

capabilities for editing geometric entities (such as points, meshes, and NURB patches).

**4.2 Examples for hands-on evaluations** 

does not support parametric solid modeling using scanned data.

Table 2. Software selected for hands-on evaluations

Model 1 *Block* 

Scanned data 634,957 points 589,693

(inch)

Table 3. Examples selected for hands-on evaluations

Dimensions 5×3×0.5

**4.3 Round 1: Auto surfacing** 

Model Pictures Based on the evaluations, we found that all software tools evaluated are able to support surface modeling either fully automatically or close to fully automation. Table 4 summarizes the test results. The results show that *Geomagic* is the only software that is able to create surface models for all five examples automatically, without any user interventions. *Rapidform* comes close second. *Rapidform* is able to construct surface models for two out of the five examples fully automatically. For the remaining three examples, only minor interventions or editing from the user are required. However, *SolidWorks* and *Wildfire* are able to support only some of the examples even after spending long hours. It took extremely long time using *SolidWorks* or *Wildfire* to process some of the examples, and yet without achieving meaningful results. Software crashed without giving warning message while conducting triangulation or surface fitting. The size of the scanned data also presents problems for *SolidWorks* and *Wildfire*. They are able to support only up to about 300,000 data points. The software becomes unstable or even crashes while handling more data points.


Table 4. Results of Round 1 evaluations

A Review on Shape Engineering and Design Parameterization in Reverse Engineering 173

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

Fig. 9. Results of the *tubing* example tested using *Geomagic*, (a) polygon mesh (589,693

Fig. 10. Results of the sheet metal example tested using *Geomagic*, (a) polygon mesh (126,492

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* 

*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

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.

triangles), (b) NURB model (1,107 patches), and (c) deviation analysis

triangles), (b) NURB model (91 patches), and (c) deviation analysis

reconstruction.

**4.3.2** *Rapidform XOR3* 

*Network* (without mesh segmentation).

to incorporation of mesh segmentation.

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.
