IfcTessellatedFaceSet

BACnet MVD

#### IfcTessellatedFaceSet

Natural language names

| tesselliertes Element aus Flächen
| Tessellated Face Set
| Ensemble de faces tessellées

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC2x3 to IFC4
IfcTessellatedFaceSet |  |  | ADDED |

##### Semantic definitions at the entity

Entity definition

The IfcTessellatedFaceSet is a boundary representation topological model limited to planar faces and straight edges. It may represent an approximation of an analytical surface or solid that may be provided in addition to its tessellation as a separate shape representation. The IfcTessellatedFaceSet provides a compact data representation of an connected face set using indices into ordered lists of vertices, normals, colours, and texture maps.

> NOTE The compact representation has been chosen to enable small data sets despite potentially large sets of faces, edges and vertices needed to represent tessellations of analyticals surfaces and solids, and despite large sets of colour and texture information to annotate the tessellated faces.

The IfcTessellatedFaceSet is an abstract supertype of tesselated face sets each imposing specific constraints on face generation for tessellation, such as triangulation (with or without strip and fans), or quadrilaterals, or polygonal faces (with or without inner loops).

> NOTE Not all different constraints on face sets are included as specific subtypes in this release of the specification.

The following attributes apply to all subtypes:

- The Coordinates are the ordered list of Cartesian points representing the vertices of the tessellated item. An index list, defined at the level of subtypes, uses the points, identified by index position, to construct the polylines that represent the faces.
- The HasColours inverse relation provides an indexed colour map with an corresponding list of indices providing a colour for each face of the tessellated face set.
- The HasTextures inverse relation provides an indexed texture map with an corresponding list of indices providing texture coordinates that map to the geometric coordinates of the polylines representing the faces.

Each face of the tessellated face set shall have:

- at least three non-coincident vertices;
- vertices that define a planar polygon;
- vertices that define a non-self-intersecting polygon.

> NOTE The definition of IfcTessellatedFaceSet is based on the indexedFaceSet defined in ISO/IEC 19775-1

> HISTORY New entity in IFC4.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
1 | Coordinates | IfcCartesianPointList3D |  | An ordered list of Cartesian points used by the coordinate index defined at the subtypes of IfcTessellatedFaceSet. | X | X
| HasColours | IfcIndexedColourMap @MappedTo | S[0:1] | Reference to the indexed colour map providing the corresponding colour RGB values to the faces of the subtypes of IfcTessellatedFaceSet. | X | X
| HasTextures | IfcIndexedTextureMap @MappedTo | S[0:?] | Reference to the indexed texture map providing the corresponding texture coordinates to the vertices bounding the faces of the subtypes of IfcTessellatedFaceSet. | X | X
| Dim :=3 | IfcDimensionCount |  | The space dimensionality of this geometric representation item, it is always 3. | 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
IfcTessellatedItem
IfcTessellatedFaceSet
1 | Coordinates | IfcCartesianPointList3D |  | An ordered list of Cartesian points used by the coordinate index defined at the subtypes of IfcTessellatedFaceSet. | X | X
| HasColours | IfcIndexedColourMap @MappedTo | S[0:1] | Reference to the indexed colour map providing the corresponding colour RGB values to the faces of the subtypes of IfcTessellatedFaceSet. | X | X
| HasTextures | IfcIndexedTextureMap @MappedTo | S[0:?] | Reference to the indexed texture map providing the corresponding texture coordinates to the vertices bounding the faces of the subtypes of IfcTessellatedFaceSet. | X | X
| Dim :=3 | IfcDimensionCount |  | The space dimensionality of this geometric representation item, it is always 3. | X | X

##### Formal representations

XML Specification
`<xs:element name="IfcTessellatedFaceSet" type="ifc:IfcTessellatedFaceSet" abstract="true" substitutionGroup="ifc:IfcTessellatedItem" nillable="true"/>
<xs:complexType name="IfcTessellatedFaceSet" abstract="true">
<xs:complexContent>
<xs:extension base="ifc:IfcTessellatedItem">
<xs:sequence>
<xs:element name="Coordinates" type="ifc:IfcCartesianPointList3D" nillable="true"/>
<xs:element name="HasColours" type="ifc:IfcIndexedColourMap" nillable="true" minOccurs="0" maxOccurs="1"/>
<xs:element name="HasTextures" nillable="true" minOccurs="0">
<xs:complexType>
<xs:sequence>
<xs:element ref="ifc:IfcIndexedTextureMap" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute ref="ifc:itemType" fixed="ifc:IfcIndexedTextureMap"/>
<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 IfcTessellatedFaceSet
ABSTRACT SUPERTYPE OF(ONEOF(IfcPolygonalFaceSet, IfcTriangulatedFaceSet))
SUBTYPE OF (IfcTessellatedItem);
Coordinates : IfcCartesianPointList3D;
INVERSE
HasColours : SET [0:1] OF IfcIndexedColourMap FOR MappedTo;
HasTextures : SET [0:?] OF IfcIndexedTextureMap FOR MappedTo;
DERIVE
Dim : IfcDimensionCount := 3;
END_ENTITY;

EXPRESS-G diagram

`

References: IfcBooleanOperand IfcIndexedColourMap IfcIndexedTextureMap

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