What is Retopologizing?  

In today’s world, few objects are simple enough to be reverse engineered from only a handful of accurate measurements.  The complexity and range of manufacturing methods produces objects that rely heavily on organic shapes for both form and function. To reverse engineer these non-mechanical shapes, retopologizing is the method of choice.  Retopologizing is the process of resurfacing an existing model using quad-based SubDs. You may want to modify an existing CAD model that no longer has a creation history, clean up a scanned mesh so it can be converted to a CAD model for manufacturing, or simplify an existing SubD mesh for real-time simulations.  Modifications on the original can also be easier when working with a SubD mesh rather than its CAD counterpart.

What can be Retopologized?

Power Surfacing RE is full of tools and features that will allow you to retopologize scanned meshes. These same tools can help you to retopologize existing SOLIDWORKS features and other CAD objects. Additionally, you can ‘retopo’ imported .obj and .stl files for both backwards engineering and for making modifications.  

The left image below shows an unprocessed scanned mesh. The image on the right shows a cleaned up scanned mesh.

Retopologizing vs. Constraints

Although you can use an existing CAD model as your reference mesh, you may be better off using Power Surfacing’s constraint system. If the CAD model is an analytic, such as a cylinder, the constraint system will provide more accuracy because the SubD faces and edges can be constrained to an extracted CAD surface or edge. When using a reference mesh for retopo, there is no concept of defining an edge and staying constrained to it. The exception is reference meshes that have open edges.  

With the retopo workflow on CAD objects, the SubD can be used to create a solid, but at the expense of accuracy.  If accuracy is not crucial and the Interpolation option is not used, the SubD will be much easier to modify or alter. The constraint system is a good way to ensure an accurate connection to an analytic shape, but may require replacing of surfaces, defining the connection shape, trimming and knitting to bring the altered object back into solid form. See Constraints in the Power Surfacing documentation for more information on their use in the modeling workflow.

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