IfcCurveSegment2D

Item	SPF	XML	Change	Description
IFC4x1 Release Candidate 1
IfcCurveSegment2D			ADDED

Semantic definitions at the entity

Entity definition

The abstract definition of a bounded 2D curve representation item. Each curve segment is defined by a start point, a start direction, a segment length and additional curve geometry parameter. It defines arcs without the need to use a trimmed curve.

NOTE Such 2D curves are used in particular by horizontal alignment segments.

Attribute definitions

#	Attribute	Type	Description	G
1	StartPoint	IfcCartesianPoint	The start point of the 2D curve as x/y coordinates defined by a 2D Cartesian point.	X
2	StartDirection	IfcPlaneAngleMeasure	The direction of the tangent at the start point. Direction value 0. indicates a curve with a start tangent along the positive x-axis. Values increases counter-clockwise, and decreases clockwise. Depending on the plane angle unit, either degree or radians, the sensible range is -360° ≤ n ≤ 360° (or -2π ≤ n ≤ 2π). Values larger then a full circle (>\|360°\| or >\|2 π\| shall not be used.	X
3	SegmentLength	IfcPositiveLengthMeasure	The length along the curve	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
IfcRepresentationItem
	LayerAssignment	IfcPresentationLayerAssignment @AssignedItems	S[0:1]	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.	X
	StyledByItem	IfcStyledItem @Item	S[0:1]	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.	X
IfcGeometricRepresentationItem
IfcCurve
	Dim :=IfcCurveDim(SELF)	IfcDimensionCount		The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.	X
IfcBoundedCurve
IfcCurveSegment2D
1	StartPoint	IfcCartesianPoint		The start point of the 2D curve as x/y coordinates defined by a 2D Cartesian point.	X
2	StartDirection	IfcPlaneAngleMeasure		The direction of the tangent at the start point. Direction value 0. indicates a curve with a start tangent along the positive x-axis. Values increases counter-clockwise, and decreases clockwise. Depending on the plane angle unit, either degree or radians, the sensible range is -360° ≤ n ≤ 360° (or -2π ≤ n ≤ 2π). Values larger then a full circle (>\|360°\| or >\|2 π\| shall not be used.	X
3	SegmentLength	IfcPositiveLengthMeasure		The length along the curve	X

Formal representations

XML Specification

 <xs:element name="IfcCurveSegment2D" type="ifc:IfcCurveSegment2D" abstract="true" substitutionGroup="ifc:IfcBoundedCurve" nillable="true"/>

 <xs:complexType name="IfcCurveSegment2D" abstract="true">

  <xs:complexContent>

   <xs:extension base="ifc:IfcBoundedCurve">

    <xs:sequence>

     <xs:element name="StartPoint" type="ifc:IfcCartesianPoint" nillable="true"/>

    </xs:sequence>

    <xs:attribute name="StartDirection" type="ifc:IfcPlaneAngleMeasure" use="optional"/>

    <xs:attribute name="SegmentLength" type="ifc:IfcPositiveLengthMeasure" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcCurveSegment2D

 ABSTRACT SUPERTYPE OF(ONEOF(IfcCircularArcSegment2D, IfcLineSegment2D, IfcTransitionCurveSegment2D))

 SUBTYPE OF (IfcBoundedCurve);

  StartPoint : IfcCartesianPoint;

  StartDirection : IfcPlaneAngleMeasure;

  SegmentLength : IfcPositiveLengthMeasure;

END_ENTITY;

 EXPRESS-G diagram