IfcSurface

BACnet MVD

#### IfcSurface

Natural language names

| Oberfläche
| Surface
| Surface

##### Semantic definitions at the entity

Entity definition

An IfcSurface is a 2-dimensional representation item positioned in 3-dimensional space. 2-dimensional means that each point at the surface can be defined by a 2-dimensional coordinate system, usually by u and v coordinates.

> NOTE Definition according to ISO/CD 10303-42:1992
> A surface can be envisioned as a set of connected points in 3-dimensional space which is always locally 2-dimensional, but need not be a manifold.

> NOTE Entity adapted from surface defined in ISO 10303-42.

> HISTORY New entity in IFC1.5

Informal Propositions:

1. A surface has non zero area.
2. A surface is arcwise connected.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---

Dim
:=3

IfcDimensionCount

The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.

> IFC4 CHANGE Derived attribute promoted from subtypes.

X

X

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
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.

> IFC2x3 CHANGE The inverse attribute LayerAssignments has been added.

> IFC4 CHANGE The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.

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.

> IFC2x3 CHANGE The inverse attribute StyledByItem has been added.

X

X

IfcGeometricRepresentationItem
IfcSurface

Dim
:=3

IfcDimensionCount

The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.

> IFC4 CHANGE Derived attribute promoted from subtypes.

X

X

##### Formal representations

XML Specification
`<xs:element name="IfcSurface" type="ifc:IfcSurface" abstract="true" substitutionGroup="ifc:IfcGeometricRepresentationItem" nillable="true"/>
<xs:complexType name="IfcSurface" abstract="true">
<xs:complexContent>
<xs:extension base="ifc:IfcGeometricRepresentationItem"/>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcSurface
ABSTRACT SUPERTYPE OF(ONEOF(IfcBoundedSurface, IfcElementarySurface, IfcSweptSurface))
SUBTYPE OF (IfcGeometricRepresentationItem);
DERIVE
Dim : IfcDimensionCount := 3;
END_ENTITY;

EXPRESS-G diagram

`

References: IfcSurfaceOrFaceSurface IfcHalfSpaceSolid IfcSurfaceCurveSweptAreaSolid IfcGeometricSetSelect IfcCompositeCurveOnSurface IfcCurveBoundedSurface IfcPcurve IfcPointOnSurface IfcRectangularTrimmedSurface IfcSurfaceCurve IfcFaceSurface

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