IFC 4.3.0.1 (IFC4X3_TC1)

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 three-dimensional position coordinate system placed within the object coordinate system of an element.

axis1 placement
Figure 8.9.3.18.A — Circle layout

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

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.

IfcCurveDim(SELF)

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.

Table 8.9.3.18.B

8.9.3.18.4 Formal representation

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

8.9.3.18.5 References