IFC (IFC4X3_ADD2) under development IfcCurveSegment Semantic definition

A type of segment positioned along a curve cutting a segment from the parent curve. If the segment is placed through IfcAxis2PlacementLinear, the positioning curve (Placement.Location.BasisCurve) does not necessarily correspond with the ParentCurve.

Informal Propositions

  1. For the foreseeable future, until implementer agreements have resulted in a defined parametric space for all possible types in attribute ParentCurve, the values for attributes SegmentStart and SegmentStart shall be of type IfcLengthMeasure. 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.

IfcSegment (3)
1 Transition IfcTransitionCode

Connectivity between the continuous segments is not enforced per se to be tangential. Setting "TangentialContinuity" to True means that the current segment shall continue with tangential continuity to the previous one.

UsingCurves SET [1:?] OF IfcCompositeCurve FOR Segments

The set of composite curves which use this composite curve segment as a segment. This set shall not be empty.

* Dim IfcDimensionCount

This attribute is formally derived.


The space dimensionality of this abstract class, handled by a function specific for concrete subtypes which returns the dimensionality of the ParentCurve attribute (defined on both subtypes).

Click to show 5 hidden inherited attributes Click to hide 5 inherited attributes
IfcCurveSegment (4)
2 Placement IfcPlacement

Placement in the context of the curve using this segment. As insertion point SegmentStart is the reference point of Placement. RefDirection of Placement also specifies the sense of the trimmed segment of ParentCurve. RefDirection is bound to the parametrization sense of the segment.

3 SegmentStart IfcCurveMeasureSelect

First trimming point of the curve segment on the ParentCurve. This point is used as the insertion point into the segmented, gradient or composite curve using this segment.

4 SegmentLength IfcCurveMeasureSelect

Length of segment measured as length or parameter value from SegmentStart. The sign of this value defines the sense agreement.

5 ParentCurve IfcCurve

Curve to be used as base for the segment definition.

Table Examples Formal representation

ENTITY IfcCurveSegment
 SUBTYPE OF (IfcSegment);
	Placement : IfcPlacement;
	SegmentStart : IfcCurveMeasureSelect;
	SegmentLength : IfcCurveMeasureSelect;
	ParentCurve : IfcCurve;
END_ENTITY; References

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