IfcCircle

ifccirel是由一组与中心距离相等的点组成的曲线。

注：圆弧段是通过使用IFCTrimedCurve定义的，BasicCurve是一个IFCCIRE。

下图说明了放置在元素对象坐标系内的三维位置坐标系中IfcCircle的定义。

 

注：定义根据ISO/CD 10303-42:1992

圆由半径、圆的位置和方向定义。数据解释如下：

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

 

圆参数化:

 

 

参数化范围为0≤u≤2π（0≤u≤360度）。

在上面定义的放置坐标系中，圆是方程C=0，其中

 

圆在任何一点的正方向都在该点曲线的切线方向T上，其中

 

注：实体改编自ISO 10303-42中定义的圆圈

IFC1.0中增加的新实体

 

 

#	Attribute	Type	Cardinality	Description	C
IfcRepresentationItem
	LayerAssignment	IfcPresentationLayerAssignment @AssignedItems	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.	X
	StyledByItem	IfcStyledItem @Item	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.	X
IfcGeometricRepresentationItem
IfcCurve
	Dim :=IfcCurveDim(SELF)	IfcDimensionCount	[1:1]	The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.	X
IfcConic
1	Position	IfcAxis2Placement	[1:1]	The location and orientation of the conic. Further details of the interpretation of this attribute are given for the individual subtypes."	X
IfcCircle
2	Radius	IfcPositiveLengthMeasure	[1:1]	The radius of the circle, which shall be greater than zero.	X

EXPRESS Specification

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