One input was not extruded because it would have made an invalid surface

I seem to cant extrude a curve into a surface. Works fine if I try to extrude as solid. However when I try to booleandifference, the output created a wierd ghosted solid.

curve.3dm (28.1 KB)

Hello - please post a Rhino file with the curve in it.



One of the curves in the polycurve folds back on itself.

I found the problem by extruding the curve and using the Dir command to check normal directions. The normals for a closed surface should point out. In one portion of the extruded surface the normals point both directions which can only happen if there are multiple surfaces. Explode the surface and there are three surfaces, not one, in the problem area.

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