Today, many boat’ hulls that are designed from different CAD software contain connectivity errors, such as holes, gaps, overlaps, bumps, patch singularities, tangency defect, etc. These problems disallow the “offsetability” of the hull’s surface. This article will show you how it is possible to use reverse engineering tool to transform a tesselated surface into a proper surface. It is also suitable for STL and Scan model.
Digitized Shape Applications
The role Physical Prototyper/Clay Modeler allows you to work with scan and surface in CATIA 3DExperience:
You have access to 3DPrinting Preparation that allows you to transform a model into a tesselated model (triangles) and the Digitized Shape applications to work with this model. From these application you can transform a scan into a surface. With this role you also have access to Generative Wireframe & Surface and Shape Healing applications that allow you to create/modify the result into a proper surface.
To quickly modify a scan into a surface, you can use the PowerFit feature included in the app Digitized Shape to Surface.
First of all, you use Digitized Shape Preparation to import the scan into CATIA. You can also run a quick analysis on it to see if there is some holes in the model. Still in the same application, you extract the boundaries of the scan.
Then switch to Generative Shape Design, you can Join and Smooth the extracted curves. After that you need to create 2 lines on your model (1 vertical and 1 horizontal). These lines need to be connected to the previous extracted lines, so use the line feature with the Point-Point mode. Create a swept surface using the 2 lines as an input.
Once you have done these steps you can use the PowerFit feature inside the Digitized Shape to Surface application. The surface will be automatically created based from the scan. You can observe the difference between the scan and the surface with the Deviation Analysis tool. When you use this feature, you have to accept a deviation tolerance. In the following case, the deviation is less than 1mm, that is very low for a boat’s hull.
At the end you can offset the surface and obtain a solid hull.
You can watch the full reverse engineering process on this following video.
Surface Network feature
Another solution to transform a scan into a surface is to create a Surface Network on the scan (feature available into the Digitized Shape to Surface app). This method take more ressources and time, but it is more flexible working with the model.
Like the PowerFit feature, you start by importing and analyzing the scan then and you extract its boundaries. After that, you create several Planar sections (vertical and horizontal). This sections will create curves from scan. It is recommended to smooth the curve in the same time.
! Important ! Do not create to much planar sections, otherwise it will take to much resources from you computer; 5-10 planar sections are good enough.
When the curves are created you can merge them using the Curves Network feature. Launch the Surface Network using the curve network and the cloud as an input. The patches are automatically generated. After the surface generated you can offset it.
If the offset feature does not work it is because there is problem of connectivity in the network. The only solution to fix this is to un-patch the surface, analyze the patches, find the bad patches and recreate them using loft or fill features.
To find the bad patches, join 2 patches together, then offset the join. It is working, edit the join feature an add more patches to the selection. Continue until finding the bad patch that generate an error. Erase it and create a new one. Continue adding patches on the join until the surface is fully merged.
Find the described process in this following video here :