IFC (IFC4X3_ADD2) under development IfcSegmentedReferenceCurve Semantic definition

The IfcSegmentedReferenceCurve is a curve defined in the linear parameter space of its base curve that is set in the attribute BaseCurve. The base curve provides a basis for the positioning of the collection of IfcCurveSegment occurrences. A deviating explicit position of a curve segment (IfcCurveSegment.Placement) from the axis of the base curve produces a superelevation i.e. depression or elevation from the axis of the base curve. The superelevation rate of change is directly proportionate to the curve segment parent curve curvature gradient equation (IfcCurveSegment.ParentCurve) in the linear parameter space of the base curve. If no deviation in the position of the curve segment to the base curve axis is specified, the axes (Axis and RefDirection) directions of IfcAxis2Placement are interpolated between the initial curve segment placement and the placement of the subsequent curve segment.

The parametrization of IfcSegmentedReferenceCurve is based on the parametrization of BaseCurve and is not altered by the Segments.

Figure shows a cross section of a IfcSegmentedReferenceCurve usage for an alignmnent representation featuring cant

segmented reference curve usage
Figure — use of a segmented reference curve on a cant segment based on a gradient curve Entity inheritance Attributes

# Attribute Type Description
IfcRepresentationItem (2)
LayerAssignment SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems

Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.

StyledByItem SET [0:1] OF IfcStyledItem FOR Item

Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.

IfcCurve (1)
* Dim IfcDimensionCount

This attribute is formally derived.


The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.

IfcCompositeCurve (4)
1 Segments LIST [1:?] OF IfcSegment

The component bounded curves, their transitions and senses. The transition attribute for the last segment defines the transition between the end of the last segment and the start of the first; this transition attribute may take the value discontinuous, which indicates an open curve.

2 SelfIntersect IfcLogical

Indication of whether the curve intersects itself or not; this is for information only.

* NSegments IfcInteger

This attribute is formally derived.


The number of component curves.

* ClosedCurve IfcLogical

This attribute is formally derived.

Segments[NSegments].Transition <> Discontinuous

Indication whether the curve is closed or not; this is derived from the transition code of the last segment.

Click to show 7 hidden inherited attributes Click to hide 7 inherited attributes
IfcSegmentedReferenceCurve (2)
3 BaseCurve IfcBoundedCurve

The basis curve providing a linear reference system for the segmented curve definition.

4 EndPoint OPTIONAL IfcPlacement

An explicit end placement providing a location and orientation of the segmented reference curve termination point.

Table Examples Formal representation

ENTITY IfcSegmentedReferenceCurve
 SUBTYPE OF (IfcCompositeCurve);
	BaseCurve : IfcBoundedCurve;
	EndPoint : OPTIONAL IfcPlacement;
END_ENTITY; References

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