Why a flat NURBS loses flatness after transformation

Transforming a flat NURBS from the original spot to another place causes an issue with the flatness of the NURBS. To be precise it is sort of still flat, regarding the “Planar” component, but at the same time, its bounding box is not flat anymore. And such a box non-flatness initiates a bunch of undesirable handling to get rid of all 0-length edges of the box because I often merely need to get a bounding rectangle for a NURBS.
Why is it for NURBS? For polylines, the bounding box is always flat.

BoundingBox for NURBS.gh (14.4 KB)

This is most likely due to round-off error. The transformation involves vector-matrix multiplication, which may lead to the control points not being exactly on the same Z-coordinate, but differing somewhere in the 12th decimal or so.

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Although it’s not great for me, because I am using it excessively, I’m glad you told me. It’s good to have all the information.

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