IfcClothoidalArcSegment2D

Item	SPF	XML	Change	Description
IFC4 ADD1 to IFC4x1
IfcClothoidalArcSegment2D			ADDED

Semantic definitions at the entity

Entity definition

The clothoidal arc segment uses the inherited attributes StartPoint as the start of the clothoidal arc, StartDirection as the tangent at the start point and SegmentLength as the clothoidal arc length.

An clothoidal arc with infinite radius (radius=”NILL”), IsCcw=”false” and IsEntry=”true”	An clothoidal arc with infinite radius (radius=”NILL”), IsCcw=”true” and IsEntry=”true”

Figure 256 — Clothoidal arc segment A	Figure 257 — Clothoidal arc segment B

An clothoidal arc with IsCcw=”false” and IsEntry=”true”	An clothoidal arc with IsCcw=”true” and IsEntry=”true”

Figure 258 — Clothoidal arc segment C	Figure 259 — Clothoidal arc segment D

An clothoidal arc with IsCcw=”true” and IsEntry=”false”	An clothoidal arc with IsCcw=”false” and IsEntry=”false”

Figure 260 — Clothoidal arc segment E	Figure 261 — Clothoidal arc segment F

An clothoidal arc with IsCcw=”true” and IsEntry=”false”	An clothoidal arc with IsCcw=”false” and IsEntry=”false”

Figure 262 — Clothoidal arc segment G	Figure 263 — Clothoidal arc segment H

Attribute definitions

#	Attribute	Type	Cardinality	Description	B
4	StartRadius	IfcPositiveLengthMeasure	[0:1]	Tthe radius of the clothoidal arc at the start point. If the radius is not provided by a value, i.e. being “NIL” it is interpreted as INFINITE – the StartPoint is at the point, where the clothoid does not have a curvature.	X
5	IsCCW	IfcBoolean	[1:1]	Indication of the clothoidal arc starting counter-clockwise or clockwise. The orientation of the clothoidal arc is IsCcw=”true”, if the spiral arc goes counter-clockwise as seen from the start point and start direction, or “to the left", and with IsCcw=”false” if the spiral arc goes clockwise, or “to the right”.	X
6	IsEntry	IfcBoolean	[1:1]	Indication of the clothoidal arc starting as an entry or an exit. The change in curvature within the spiral arc from the start point, with IsEntry =”true”, if the arc of the clothoid has increasing curvature, and with IsEntry=”false”, if the arch of the clothoid has decreasing curvature.	X
7	ClothoidConstant	IfcReal	[1:1]	The constant A (not A square), that determines the rate of curvature change along the clothoid.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	B
IfcRepresentationItem
	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.	X
IfcGeometricRepresentationItem
IfcCurve
	Dim :=IfcCurveDim(SELF)	IfcDimensionCount	[1:1]	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	[1:1]	The start point of the 2D curve as x/y coordinates defined by a 2D Cartesian point.	X
2	StartDirection	IfcPlaneAngleMeasure	[1:1]	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	[1:1]	The length along the curve	X
IfcClothoidalArcSegment2D
4	StartRadius	IfcPositiveLengthMeasure	[0:1]	Tthe radius of the clothoidal arc at the start point. If the radius is not provided by a value, i.e. being “NIL” it is interpreted as INFINITE – the StartPoint is at the point, where the clothoid does not have a curvature.	X
5	IsCCW	IfcBoolean	[1:1]	Indication of the clothoidal arc starting counter-clockwise or clockwise. The orientation of the clothoidal arc is IsCcw=”true”, if the spiral arc goes counter-clockwise as seen from the start point and start direction, or “to the left", and with IsCcw=”false” if the spiral arc goes clockwise, or “to the right”.	X
6	IsEntry	IfcBoolean	[1:1]	Indication of the clothoidal arc starting as an entry or an exit. The change in curvature within the spiral arc from the start point, with IsEntry =”true”, if the arc of the clothoid has increasing curvature, and with IsEntry=”false”, if the arch of the clothoid has decreasing curvature.	X
7	ClothoidConstant	IfcReal	[1:1]	The constant A (not A square), that determines the rate of curvature change along the clothoid.	X

Formal representations

XSD Specification

 <xs:element name="IfcClothoidalArcSegment2D" type="ifc:IfcClothoidalArcSegment2D" substitutionGroup="ifc:IfcCurveSegment2D" nillable="true"/>

 <xs:complexType name="IfcClothoidalArcSegment2D">

  <xs:complexContent>

   <xs:extension base="ifc:IfcCurveSegment2D">

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

    <xs:attribute name="IsCCW" type="ifc:IfcBoolean" use="optional"/>

    <xs:attribute name="IsEntry" type="ifc:IfcBoolean" use="optional"/>

    <xs:attribute name="ClothoidConstant" type="ifc:IfcReal" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcClothoidalArcSegment2D

 SUBTYPE OF (IfcCurveSegment2D);

  StartRadius : OPTIONAL IfcPositiveLengthMeasure;

  IsCCW : IfcBoolean;

  IsEntry : IfcBoolean;

  ClothoidConstant : IfcReal;

END_ENTITY;

 EXPRESS-G diagram