8.9.3.28 IfcCurveSegment

8.9.3.28.1 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

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.

8.9.3.28.2 Entity inheritance

8.9.3.28.3 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. IFC2x3-CHANGE The inverse attribute LayerAssignments has been added. IFC4-CHANGE The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
	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. IFC2x3-CHANGE The inverse attribute StyledByItem has been added.
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. `IfcSegmentDim(SELF)` 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 8.9.3.28.D

8.9.3.28.4 Examples

Figure 8.9.3.28.A

Sectioned Solid Horizontal
Figure 8.9.3.28.B

Fixed Reference Swept Area Solid
Figure 8.9.3.28.C

Linear Placement Of Signal

8.9.3.28.5 Formal representation

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