STL export settings explanation

Jlabs

I'm a bit unclear what each of the settings in the "custom" STL export mean. It's unclear what they control (could the labels be updated to provide more insight?), and it's not in the OnShape documentation, can someone explain what each custom setting controls?

Angular deviation: From what? Is this controlling the minimum or maximum angle to determine where additional triangles are added? Is lower or higher create a higher resolution STL file?

Chordal tolerance: I can see it's in the selected units, but tolerance of what?

Minimum facet width: Is that the smallest a triangle can be? Would setting a maximum width more directly control the file resolution?

Thanks in advance

lemon1324

Usually, angular deviation puts a limit on the maximum angle between two faces (measured as angle between outward normals).  As you lower that spec, the difference between adjacent triangles approaches locally flat. Practically, lowering it gives you a higher resolution model--you'd see less faceting and more triangles in the mesh, all else equal.

thomas_buechner

Jason_66,
I am trying to understand the same settings. I was able to find a webpage that explains Chordal Tolerance pretty well.
http://www.padtinc.com/blog/additive-mfg/stl-file-tolerance-a-short-explanation-of-faceting-and-chord-height
Let me know if you get answers to the other STL settings.

lemon1324

Usually, angular deviation puts a limit on the maximum angle between two faces (measured as angle between outward normals).  As you lower that spec, the difference between adjacent triangles approaches locally flat. Practically, lowering it gives you a higher resolution model--you'd see less faceting and more triangles in the mesh, all else equal.