IfcPcurve

IfcPcurve是在其参考曲面的参数空间内定义的曲线。

注：定义根据ISO/CD 10303-42:1992

pcurve是一条基于曲面的曲线，定义在该曲面的参数空间中。基曲线是在参考基曲面的二维参数空间中定义的曲线。虽然它是由二维空间中的曲线定义的，但涉及的变量是u和v，它们出现在参考曲面的参数表示中，而不是x、y、笛卡尔坐标。基础曲线仅在曲面的参数化范围内定义。

注：实体改编自ISO 10303-42中的pcurve。

IFC4中增加的新实体。

Formal Propositions

Rule	Description
DimIs2D	The dimensionality of the parameter space curve shall be 2.

 

#	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
IfcPcurve
1	BasisSurface	IfcSurface	[1:1]		X
2	ReferenceCurve	IfcCurve	[1:1]		X

EXPRESS Specification

ENTITY IfcPcurve
 SUBTYPE OF (IfcCurve);
  BasisSurface : IfcSurface;
  ReferenceCurve : IfcCurve;
 WHERE
  DimIs2D : ReferenceCurve.Dim = 2;
END_ENTITY;