There are a number of reasons why a designer or engineer would reverse engineer a part. (We’ll define reverse engineering as fitting usable CAD data to a scan of a physical object.)
One reason is to get a completely accurate CAD representation of the physical object. Most objects are not exactly symmetrical, have imperfections, etc. Sometimes you want all that information represented in your CAD model. For instance, if you are making a custom after-market part that needs to mate to an existing physical object, you would want an accurate representation of that object.
Another reason is to reproduce in CAD the general shape of the physical object, but not care so much that the CAD file exactly represents the physical object. If this is your objective, you might assume symmetry of the object, or leave out imperfections or minor details. You might take this approach if you are going to manufacture a copy of the physical object and you have a loose tolerance, where the form and shape is more important than exactness.
A final reason is to use the scanned object as the starting point to explore a new form or variation. For example, you might scan a car hood, then use that data to make a new hood with a scoop in it.
In this webinar recorded on November 29, 2011, T-Splines user Sky Greenawalt introduces T-Splines 3.3 beta for Rhino, and shows how its new reverse engineering tools provide high quality, cost-effective solutions for each of these reasons.
Sky’s presentation is pretty expansive, ranging from discussions about shape and accuracy, to the nuts and bolts of how you actually run the commands.
Take a look at the webinar below. Your comments are welcome. You can also read the audience Q&A from the webinar.
T-Splines 3.3 is a free upgrade to anyone who has bought T-Splines v3 for Rhino.