buildingSMART Forums

IfcCompositeCurveSegment has a fault in the documentation

https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/ifccompositecurvesegment.htm
The NOTE in the Description about the parameter SameSense (" If the datatype of ParentCurve is IfcTrimmedCurve, the value of SameSense overrides the value of IfcTrimmedCurve.SenseAgreement"), makes no sense.

If the ParentCurve is a IfcTrimmedCurve of a IfcCircle, then false SameSense on IfcCompositeCurveSegment would change the resulting curve from IfcTrimmedCurve, not only change the direction of the curve, as one should expect. Why is the NOTE needed to begin with?

agreed. In particular the term “override” adds to the confusion.The parameter SameSense does change the parametric direction (ascending vs descending, or min to max vs max to min) of the parent curve, independently of the type of the parent curve.

So the note (if at all) should say: Attention, you need to consider the SameSense attribute after applying the SenseAgreement attribute to a trimmed curve.

For small documentation fixes such as these, can we encourage submitting PRs to the Git repository that hosts IFC? Perhaps we can write a little “how-to” guide?

I think the NOTE should simply be deleted, so that it doesn’t appear like IfcTrimmedCurve should be treated differently than any other curve.