Curve from surface based on direction

Using Rhino 6, I have a polysurface. Is there a way to draw contour curve(s) based on the direction? For example, I’d like to draw a line at the point where the surface normal is 45deg.

I can used the direction command and hover and see the angles and place points and try to connect lines, but I want to know if there is a smoother way to do it

Alternatively, I also have a mesh version, if there is a way to select facets based on direction, that could work as well

you can project the line on the surface and then use the _Fin command to extrude it tangent or normal to the surface, is that what you want?

Hello - use the DraftAngleAngleAnalysis to visualize the line or curve:


testSilhouette to get a curve - this is a test command and not very friendly, UI wise, and not supported but will allow you to set a draft angle at the command line if you do not pre-select the object.



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draftangleanalysis does visualize it, however I want to create a curve that I can split on.

I tried Testsilhouette but I get “111 ON_SIL_EVENT returned”