IfcPolyline

IfcPolyline是一条有界曲线，只有由笛卡尔点列表定义的直线段。如果列表中的第一个和最后一个笛卡尔点相同，则多段线为闭合曲线，否则为开放曲线。

下图演示了有界IfcPolyline，并显示了每个线段和整个多段线的参数化长度。

 

 

带参数长度的有界IfcPolyline

 

根据注释CD-03/ISO 10342定义

多段线是由n-1条直线段组成的有界曲线，由n个点、P1、P2。。。请注意。曲线的第i段参数化如下：

 

式中i-1≤u≤i且参数范围为0<≤u≤n-1。

注：实体改编自ISO 10303-42中的折线。

IFC1.0中增加的新实体

 

Formal Propositions

Rule	Description
SameDim	The space dimensionality of all Points shall be the same.

 

 

 

 

#	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
IfcBoundedCurve
IfcPolyline
1	Points	IfcCartesianPoint	L[2:?]	The points defining the polyline.	X

EXPRESS Specification

ENTITY IfcPolyline
 SUBTYPE OF (IfcBoundedCurve);
  Points : LIST [2:?] OF IfcCartesianPoint;
 WHERE
  SameDim : SIZEOF(QUERY(Temp <* Points | Temp.Dim <> Points[1].Dim)) = 0;
END_ENTITY;