IfcFaceBasedSurfaceModel

BACnet MVD

#### IfcFaceBasedSurfaceModel

Natural language names

| Flächenmodell (basierend auf Einzelflächen)
| Face Based Surface Model

##### Semantic definitions at the entity

Entity definition

The IfcFaceBasedSurfaceModel represents the a shape by connected face sets. The connected faces have a dimensionality 2 and are placed in a coordinate space of dimensionality 3.

> NOTE Definition according to ISO/CD 10303-42:1992
> A face based surface model is described by a set of connected face sets of dimensionality 2. The connected face sets shall not intersect except at edges and vertices, except that a face in one connected face set may overlap a face in another connected face set, provided the face boundaries are identical. There shall be at least one connected face set.
> A connected face set may exist independently of a surface model.

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

> HISTORY New entity in IFC2x.

Informal Propositions:

1. The connected face sets shall not overlap or intersect except at common faces, edges or vertices.
2. The fbsm faces have dimensionality 2.

> IFC4 CHANGE The entity has been deprecated and shall not be used. The entity IfcFacetedBrep shall be used instead.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
1 | FbsmFaces | IfcConnectedFaceSet | S[1:?] | The set of connected face sets comprising the face based surface model. |  | X
| Dim :=3 | IfcDimensionCount |  | The space dimensionality of this class, it is always 3. |  | 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
IfcFaceBasedSurfaceModel
1 | FbsmFaces | IfcConnectedFaceSet | S[1:?] | The set of connected face sets comprising the face based surface model. |  | X
| Dim :=3 | IfcDimensionCount |  | The space dimensionality of this class, it is always 3. |  | X

##### Examples

- Surface model

##### Formal representations

XML Specification
`<xs:element name="IfcFaceBasedSurfaceModel" type="ifc:IfcFaceBasedSurfaceModel" substitutionGroup="ifc:IfcGeometricRepresentationItem" nillable="true"/>
<xs:complexType name="IfcFaceBasedSurfaceModel">
<xs:complexContent>
<xs:extension base="ifc:IfcGeometricRepresentationItem">
<xs:sequence>
<xs:element name="FbsmFaces">
<xs:complexType>
<xs:sequence>
<xs:element ref="ifc:IfcConnectedFaceSet" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute ref="ifc:itemType" fixed="ifc:IfcConnectedFaceSet"/>
<xs:attribute ref="ifc:cType" fixed="set"/>
<xs:attribute ref="ifc:arraySize" use="optional"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcFaceBasedSurfaceModel
SUBTYPE OF (IfcGeometricRepresentationItem);
FbsmFaces : SET [1:?] OF IfcConnectedFaceSet;
DERIVE
Dim : IfcDimensionCount := 3;
END_ENTITY;

EXPRESS-G diagram

`

References: IfcSurfaceOrFaceSurface

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