After creating a closed polyline (the ends are arcs), according to the C3D API, set the elevation from the surface, but at the end arc, the number of elevation points is small, and the arc does not appear to be round. How to set the elevation in the arc Where to increase the elevation point?
Probably the current setting for Curve tesselation is not suitable for your requirements.
this is much easier to find out if you share your drawing (just the polyline and the surface).
I set the element line elevation from the surface on the C3D panel. The number of end arc elevation points is satisfactory, but when I call this API to achieve this by programming, there are fewer end elevation points.
Ok, your question is API related.
Then better ask in the Civil 3D Customisation forum
https://forums.autodesk.com/t5/civil-3d-customization/bd-p/190
Best you post the useful portions of your code as example. Sometimes only needed settings are missing.
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