Natural language names
Semantic definitions at the entity
Entity definition

An IfcCircle is a curve consisting of a set of points having equal distance from the center.

NOTE  A circular arc segment is defined by using the IfcTrimmedCurve with BasisCurve being an IfcCircle or alternatively as a circular arc defined by three points within an IfcIndexedPolyCurve.

Figure 388 illustrates the definition of IfcCircle within a three-dimensional position coordinate system placed within the object coordinate system of an element.

axis1 placement

Figure 388 — Circle layout

The IfcCircle ia parameterized using numeric values in correspondence to the plane angle unit provided within the IfcUnitAssignment. If the plane angle unit is 'Degree' the parametric range of a circle is 0 ≤ u ≤ 360, if the plane angle unit is radians, the parametric range is 0 ≤ u ≤ 2π.


NOTE Definition according to ISO/CD 10303-42:1992
A circle is defined by a radius and the location and orientation of the circle. Interpretation of data should be as follows:
C = SELF\IfcConic.Position.Location
x = SELF\IfcConic.Position.P[1]
y = SELF\IfcConic.Position.P[2]
z = SELF\IfcConic.Position.P[3]
R = Radius

and the circle is parameterized as


The parameterization range is 0 ≤ u ≤ 360 degree, u is an angular parameter and when a numerical value is specified it shall use the current units for plane angle measure. In the placement coordinate system defined above, the circle is the equation C = 0, where


The positive sense of the circle at any point is in the tangent direction, T, to the curve at the point, where

NOTE  Entity adapted from circle defined in ISO 10303-42
HISTORY  New entity in IFC1.0
Attribute definitions
#AttributeTypeCardinalityDescription G
2RadiusIfcPositiveLengthMeasure The radius of the circle, which shall be greater than zero.X
Inherited definitions from supertypes
Entity inheritance IfcConic IfcCurve IfcGeometricRepresentationItem IfcRepresentationItem
Attribute inheritance
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.
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.
IfcDimensionCountThe space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve. X
1PositionIfcAxis2Placement The location and orientation of the conic. Further details of the interpretation of this attribute are given for the individual subtypes." X
2RadiusIfcPositiveLengthMeasure The radius of the circle, which shall be greater than zero.X
Formal representations
XML Specification
 <xs:element name="IfcCircle" type="ifc:IfcCircle" substitutionGroup="ifc:IfcConic" nillable="true"/>
 <xs:complexType name="IfcCircle">
   <xs:extension base="ifc:IfcConic">
    <xs:attribute name="Radius" type="ifc:IfcPositiveLengthMeasure" use="optional"/>
EXPRESS Specification
ENTITY IfcCircle
 SUBTYPE OF (IfcConic);
  Radius : IfcPositiveLengthMeasure;

Link to EXPRESS-G diagram EXPRESS-G diagram

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