Geometry_Engine: NurbsSurface.Degrees is not Correct for Closed Surfaces

[enarhi]

Description:

NurbsSurface.Degrees is returning the wrong value for closed NurbsSurfaces, causing a breaking error when the NurbsSurface is read in Dynamo (and potentially elsewhere).

How to replicate:

Any closed nurbssurface will return degrees of 1 in the closed direction as a result of this bug as shown below.

Expected behaviour:

Degrees should return 3 for U and V. NurbsSurface.Degrees should not rely on repeated Knots at the start to deduce degrees. A potential fix could be querying control points for repeated control points which can indicate a closed surface.

Test file(s):

Test File

[enarhi]

@epignatelli assigning you to get your eyes on this, go ahead and pass along as you see fit. Hoping we can sort it out without an oM change.

[enarhi]

Added a sphere test case to the test file as this looks to be effectively a third case. The current definition of NurbsSurface does not translate correctly for a sphere in Rhino either, as shown below. May need to create a separate issue for this in the Rhinoceros_Toolkit.

[epignatelli]

Thanks @enarhi, I am passing this to @pawelbaran, he should be able to solve the problem.