Merging and aligning a scan in Geomagic Studio 11

In my duties as Product Specialist, I am part of the main entry point for customers with technical questions or problems. The Tips and tricks section aims to present questions (and solutions!) taken from everyday life asked by some of our customers. In order to help a large number of people, we aim here to explain the questions as well as the answers provided.

I recently received a question merging scans of a car in order then extract the symmetry plane of the resulting scan. Using Geomagic Studio 11 this task is pretty simple and is presented below. In this case, we assume that we have several scans which have to be merged together (for example, if the body of the car and the wheels were scanned separately).

1. Clean each partial STL and make sure you have only relevant data (i.e. remove the blocks under the wheels and noise which might be floating around). In order to clean noise easily, it is possible to use the Open Manifold command.

   

2. Since the scans were scanned in the same referential with the Handyscan 3D, there is no need for an external alignment of the different scans together. When each scan is imported in Geomagic Studio, they will already be correctly aligned, but will be present as separate objects.
3. Try to make sure that you have as less overlap as possible in order to minimize the risks of having overlapping layers of scan which might cause problems during the merge of the scans. This is especially true when you have scans with different resolutions (e.g. coarse resolution on the car body and a higher resolution mesh for the wheels).
4. In order to merge the scans together, what we usually use is the function Merge, located in Polygons | Combine | Merge. When using this function, make sure that Global Registration is unchecked (as the registration is already done directly in the scan) and that point spacing is check with an appropriate value for your STL. This will sample the points on the surface and rewrap it in order to make smooth transitions. Some adjustments might be needed in order to find the optimal settings for you data. Also, make sure to check Keep Original Data so you can go back to the original data in case something goes wrong.

   

5. When the scans are all merged, it is possible to create a symmetry plane. In Tools | Datum | Create Datum, there is an option for the symmetry plane. You will need to place manually a plane which would be close to the real symmetry plane of the object in order to help the software in its calculations. Then, click on Apply and Next in order to save the plane.

   

6. Finally, in order to create an alignment, you can do it directly in VxScan 3.1, if it is not to late. In the Entities menu, theAlign function will automatically put a reference system in the center of the object, relative to the main axes of your object. Then, when importing the object in Geomagic, it is important to keep it pinned and make sure that all other scans are aligned to this part. If for whatever reason doing this manipulation in VxScan is not an option, it is possible to do it in Studio with the Alignment to World function.
   1. First, 3 datums will need to be created: one plane, one line and a point. These will allow to define the orientation of the axis system.
      1. 1. If the origin has to be located at the center of the scan, the point has to be created with being the Centroid of a selection, in this case, the whole scan.

      

   2. When all the datums are created, it is now possible to align the scan to the world referential with the Tools | Alignment | To World function. Then, create pairs between the world reference system and the datums which were created earlier.

      

      The end result will be the STL file, with the symmetry plane in the middle and aligned to a coordinate system located in the middle of the scan.