8.9.3.18 IfcCircle

AbV ⓘ

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 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 A — Circle layout

{ .extDef}

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. 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.
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 B

8.9.3.18.4 Formal representation

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

8.9.3.18.5 References

IfcConic