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Creating a Composite Surface from an Imported Mesh.

malcolm_smith_1malcolm_smith_1 Member Posts: 44
I'm currently investigating Onshape for our company, to replace Autodesk Inventor. Referring to a discussion here https://forum.onshape.com/discussion/5248/recognize-stl-as-a-solid-for-use-of-full-suite-of-part-studio-tools#latest I have a need to be able to convert an imported mesh into a composite surface, mainly so that I can use the Intersection tool in a sketch to derive section curves from the surface. The only way I have found to do this so far is to use the three vertices from one element of the mesh to define a plane, do a sketch on the plane of a triangle defined by the three vertices and use that to create a small surface. You would need to do that for every element on the surface to convert the whole mesh. Is this something that could be done using FeatureScript? Maybe the script could have an option to select an area of the mesh, rather than the whole mesh, to reduce computation time?


  • joe_dunnejoe_dunne Onshape Employees, Developers Posts: 152
    Malcom PowerSurface in the App Store has the ability to create smooth surfaces over mesh data and bring into Onshape

    Joe Dunne / Onshape, Inc.
  • malcolm_smith_1malcolm_smith_1 Member Posts: 44
    Thanks Joe, I'll check it out.
  • malcolm_smith_1malcolm_smith_1 Member Posts: 44
    I did check out PowerSurface. Looks good as a surface modelling tool, however, it's a complicated and expensive (for a large mesh) way to do something which I feel should be a standard tool in Onshape. Explicitly, all I want to do is to be able find the intersection between a plane and a mesh and draw that in a sketch on the plane. Perhaps rather than converting a mesh to a surface, Feature Script might be able to locate the mesh vertices immediately either side of the intersecting plane an find the point of intersection between the lines connecting those points and the plane. Can FeatureScript do this sort of thing,or is it more of a macro language using existing commands?
  • mahirmahir Member, Developers Posts: 1,017 ✭✭✭✭
    edited June 2018
    @malcolm_smith_1, I'm not sure what kind of access FS has to internal mesh data, but it can definitely help to at least semi-automate the process of creating surfaces. Here is how I would envision the FS working.
    1. Start the Faceted Surface FS
    2. Select 3 or more points from a mesh body in a "daisy chain", each successive point connected to the last via a line segment.
    3. A plane is generated using the first 3 points
    4. A triangle is sketched on that plane using the same 3 points
    5. That triangular sketch region is offset/copied to create a surface
    6. Each additional point generates a new triangular surface when matched with the preceding 2 points
    If FS has access to the STL/mesh data, then the whole process could be automated by selecting the mesh body, since I believe STL files group vertices in such a way that facet surface location/orientation can be inferred. But I don't know enough about the inner workings of FS and/or the OS API to say whether that's doable or not.

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