IfcFacetedBrepWithVoids

IfcFacetedBrepWithVoids是刻面B-rep的一个特化，它的内部包含一个或多个空洞。空隙被表示为闭合壳，这些壳被定义为使壳法线指向空洞。

注：实体根据ISO 10303-42中定义的brep_，带有_空隙和镶嵌面_brep。

IFC1.0中增加的新实体

IFC4 修改子类型从IfcManifoldSolidBrep更改为IfcFacetedBrep，具有对基于文件的交换的向上兼容性。

非正式提议：

①每个空壳应与外壳和其他空壳分离

②每个空心外壳应封闭在外壳内，而不是任何其他空心外壳内。尤其是外壳不在空壳组中

③IfcManifoldSolidBrep中的每个shell只能引用一次。

④IfcFacetedBrep中所有壳体表面的所有边界环应为IfcPolyLoop类型。

#	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
IfcSolidModel
	Dim :=3	IfcDimensionCount	[1:1]	The space dimensionality of this class, it is always 3.	X
IfcManifoldSolidBrep
1	Outer	IfcClosedShell	[1:1]	A closed shell defining the exterior boundary of the solid. The shell normal shall point away from the interior of the solid.	X
IfcFacetedBrep
IfcFacetedBrepWithVoids
2	Voids	IfcClosedShell	S[1:?]	Set of closed shells defining voids within the solid.	X

EXPRESS Specification

ENTITY IfcFacetedBrepWithVoids
 SUBTYPE OF (IfcFacetedBrep);
  Voids : SET [1:?] OF IfcClosedShell;
END_ENTITY;