IFC 4.3.x development IfcCircle Semantic definitions at the entity

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.

Figure 1 illustrates the definition of IfcCircle within a three-dimensional position coordinate system placed within the object coordinate system of an element.

"axis1 placement"


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 ≤ 2π (0 ≤ u ≤ 360 degree).
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 Attributes

# Attribute Type Description
LayerAssignmentSET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment 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.
Dim INVALID The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.
1 Position IfcAxis2Placement The location and orientation of the conic. Further details of the interpretation of this attribute are given for the individual subtypes."
2 Radius IfcPositiveLengthMeasure The radius of the circle, which shall be greater than zero. Entity inheritance

dot_inheritance IfcCircle IfcCircle IfcConic IfcConic IfcCircle->IfcConic IfcEllipse IfcEllipse IfcEllipse->IfcConic IfcCurve IfcCurve IfcConic->IfcCurve IfcCurve_children 7 more... IfcCurve_children->IfcCurve IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcCurve->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem Formal representations

ENTITY IfcCircle
 SUBTYPE OF (IfcConic);
	Radius : IfcPositiveLengthMeasure;