ifc曲面是位于三维空间中的二维表示项。二维意味着曲面上的每个点都可以由二维坐标系定义，通常由u和v坐标确定。
注：定义根据ISO/CD 10303-42:1992
曲面可以想象为三维空间中的一组连通点，它通常是局部二维的，但不必是流形。
注：实体改编自ISO 10303-42中定义的表面。
IFC1.5中增加的新实体
非正式提议：
①曲面具有非零面积。
②曲面呈弧形连接。
| # | 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 | |
EXPRESS Specification
ENTITY IfcSurface
ABSTRACT SUPERTYPE OF(ONEOF(IfcBoundedSurface, IfcElementarySurface, IfcSweptSurface))
SUBTYPE OF (IfcGeometricRepresentationItem);
DERIVE
Dim : IfcDimensionCount := 3;
END_ENTITY;