8.9.3.18 IfcCircle
8.9.3.18.1 Semantic definition
An IfcCircle is a curve consisting of a set of points having equal distance from the center.
Figure 8.9.3.18.A illustrates the definition of IfcCircle within a threedimensional position coordinate system placed within the object coordinate system of an element.
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
The circle is parameterized as
$$ \lambda(u) = C + R(\cos(u)x + \sin(u)y) $$
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
$$ C(x,y,z) = x^2 + y^2  R^2 $$
The positive sense of the circle at any point is in the tangent direction, T, to the curve at the point, where
$$ T = (C_y,C_x,0) $$
8.9.3.18.2 Entity inheritance

 IfcCurve
 IfcAnnotationFillArea
 IfcBooleanResult
 IfcBoundingBox
 IfcCartesianPointList
 IfcCartesianTransformationOperator
 IfcCsgPrimitive3D
 IfcDirection
 IfcFaceBasedSurfaceModel
 IfcFillAreaStyleHatching
 IfcFillAreaStyleTiles
 IfcGeometricSet
 IfcHalfSpaceSolid
 IfcLightSource
 IfcPlacement
 IfcPlanarExtent
 IfcPoint
 IfcSectionedSpine
 IfcSegment
 IfcShellBasedSurfaceModel
 IfcSolidModel
 IfcSurface
 IfcTessellatedItem
 IfcTextLiteral
 IfcVector
8.9.3.18.3 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. 

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. 

IfcCurve (1)  
*  Dim  IfcDimensionCount 
This attribute is formally derived.
The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve. 
IfcConic (1)  
1  Position  IfcAxis2Placement 
The location and orientation of the conic. Further details of the interpretation of this attribute are given for the individual subtypes." 
Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes  
IfcCircle (1)  
2  Radius  IfcPositiveLengthMeasure 
The radius of the circle, which shall be greater than zero. 
8.9.3.18.4 Examples
8.9.3.18.5 Formal representation
ENTITY IfcCircle
SUBTYPE OF (IfcConic);
Radius : IfcPositiveLengthMeasure;
END_ENTITY;