Get projection of vector field along normals from an imported STL file, and use it in the Calculator


I would like to get the velocity component of a flow field along the local normals and perps of an imported STL mesh.

  1. The pipeline is illustrated in the attached picture. A dummy model is used, the STL mesh is a plane but could have arbitrary shape.

After importing the STL file, “Resample with Dataset” is used to map the results on the STL mesh.
From there “Normal Glyphs” are used to define the Normals of the imported STL mesh.
But I am missing how to proceed to get the normals in the Calculator in order to compute the velocity projection along these normals and perpandiculars.

  1. “Surface Vectors”, or “GenerateSurfaceNormals” should do the job too. Shown as Glyphs the produced results have nothing to do with the direction of the imported STL, so I am missing a step here too.

The similar topics are

but cannot figure out how to apply in this context

Thank you in advance

Generate Surface Normals should be the right thing to do. In fact, Normal Glyphs is a compound filter that uses Generate Surface Normals internally, so it makes little sense that one would work and the other would not.

Can you be more specific about how the result is wrong? Can you perhaps share your STL data for us to take a look?

Thank you for your feedback. I’ll try to be more specific: whether I apply one or the other method, there is no ‘’ Normals ‘’ available in the calculator, so I cannot proceed with the calculations I would like to do.

channel-Mesh.stl (609.8 KB)
Please find attached the STL file as requested

“Normal Glyphs” is a display filter so it makes sense there is no “Normals” in the “Calculator”. “GenerateSurfaceNormals” leads to the correct results when visualised properly together with the Glyph filter. Happy to close this topic, thank you for you time.