Add IfcCompositeCurve as possible reference for IfcOffsetCurveByDistances in IfcAlignment spec#971
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RickBrice wants to merge 1 commit into
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Add IfcCompositeCurve as possible reference for IfcOffsetCurveByDistances in IfcAlignment spec#971RickBrice wants to merge 1 commit into
IfcCompositeCurve as possible reference for IfcOffsetCurveByDistances in IfcAlignment spec#971RickBrice wants to merge 1 commit into
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evandroAlfieri
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Apr 2, 2026
civilx64
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The initial comment on this PR is a bit confusing as it starts with "...can never be 2D".
After reading back through the linked issues and discussions the consensus is that it can be 2D (e.g. offset from IfcCompositeCurve) or 3D (e.g. offset from IfcGradientCurve) - which is reflected in this patch.
evandroAlfieri
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IfcCompositeCurve as possible reference for IfcOffsetCurveByDistances in IfcAlignment spec
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As defined, IfcOffsetCurveByDistances can never by a 2D curve. In the proposed (and subsequently withdrawn) IFC 4.2 specification IfcOffsetCurveByDistances was defined as "IfcOffsetCurveByDistances as a 2D or 3D curve defined relative to an IfcAlignmentCurve or another IfcOffsetCurveByDistances".
IfcAlignmentCurve had the property of being either 2D or 3D. This property was lost when IfcAlignmentCurve was replaced with IfcGradientCurve in IFC 4.3.
This change has been discussed in the Implementors Forum
buildingSMART/IFC4.x-IF#139
Also see
#733 for potential rules for IfcOffsetCurveByDistances