IfcSweptSurface

IfcSweptSurface是通过扫掠曲线定义的曲面。扫掠曲面由开放或闭合曲线定义，由IfcProfileDef子类型表示，IfcProfileDef是隐式平面上的二维曲线，并由扫掠操作表示。

扫掠曲线是通过在对象坐标系的xy平面上定位轮廓来定义的，

扫掠操作应用于IfcSweptSurface子类型中定义的扫掠曲线；

可选的位置坐标系允许相对于对象坐标系重新定位生成的扫描曲面。

注：定义根据ISO/CD 10303-42:1992

扫掠曲面是通过沿另一条曲线扫掠曲线而构建的曲面。

注：实体改编自ISO 10303-42中定义的扫掠表面。

IFC2x中增加的新实体。

IFC4 修改Position属性为可选，具有对基于文件的交换的向上兼容性。

#	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
IfcSurface
	Dim :=3	IfcDimensionCount	[1:1]	The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.	X
IfcSweptSurface
1	SweptCurve	IfcProfileDef	[1:1]	The curve to be swept in defining the surface. The curve is defined as a profile within the position coordinate system.	X
2	Position	IfcAxis2Placement3D	[0:1]	Position coordinate system for the swept surface, provided by a profile definition within the XY plane of the Position coordinates. If not provided, the position of the profile being swept is determined by the object coordinate system. In this case, the swept surface is not repositioned.	X

EXPRESS Specification

ENTITY IfcSweptSurface
 ABSTRACT SUPERTYPE OF(ONEOF(IfcSurfaceOfLinearExtrusion, IfcSurfaceOfRevolution))
 SUBTYPE OF (IfcSurface);
  SweptCurve : IfcProfileDef;
  Position : OPTIONAL IfcAxis2Placement3D;
 WHERE
  SweptCurveType : SweptCurve.ProfileType = IfcProfileTypeEnum.Curve;
END_ENTITY;