IfcPlane：平面是在x和y方向上的无界曲面，有界平面是用IfcBoundedSurface的子类型定义的，基本面是一个平面。
注：定义根据ISO/CD 10303-42:1992
平面是一个具有恒定法线的无界曲面。平面由平面上的一点和平面的法线方向定义。数据解释如下：
C = Position.Location
x = Position.P[1]
y = Position.P[2]
z = Position.P[3] => normal to plane
曲面参数化为：
其中参数范围为-∞<u，v<∞。在上面的参数化中，单位向量x和y的长度单位是从平面的上下文中导出的。
注：如果从负法线方向看，矩形有界平面可以由一个IfcRectangularTrimmedSurface定义，U1=左边界在x，U2=右边界在x，V1=下限在y，V2=上限在y中。（假设Usense和Vsense同意基面的意义）。
继承的属性解释为：
IFCELEMENTARY表面。位置定义平面的位置和方向。
IfcElementarySurface.Position.位置定义平面上的点。
IFCELEMENTARY表面。位置.P[3]定义平面的法线。
注：根据ISO 10303-42中的平面改编的实体。
IFC1.5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 | |||||
| IfcSurface | |||||
| Dim :=3 |
IfcDimensionCount | [1:1] | The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item. | X | |
| IfcElementarySurface | |||||
| 1 | Position | IfcAxis2Placement3D | [1:1] | The position and orientation of the surface. This attribute is used in the definition of the parameterization of the surface. | X |
| IfcPlane | |||||
EXPRESS Specification
ENTITY IfcPlane
SUBTYPE OF (IfcElementarySurface);
END_ENTITY;