#### 8.6.3.19 IfcTessellatedFaceSet

| Ensemble de faces tessellées
| tesselliertes Element aus Flächen

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.

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

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 Normals are the ordered list of directions representing normals of the tessellated item. An index list, defined at the level of subtypes, uses the directions, identified by index position, to define the normals either by face or by edge.
- 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.

XSD 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:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcTessellatedFaceSet

| ABSTRACT SUPERTYPE OF(IfcTriangulatedFaceSet)

| SUBTYPE OF (IfcTessellatedItem);

Coordinates | : | IfcCartesianPointList3D;
Normals | : | OPTIONAL LIST [1:?] OF LIST [3:3] OF IfcStrippedOptional;
Closed | : | OPTIONAL IfcStrippedOptional;

| INVERSE

END_ENTITY;

Attribute Definitions:

Coordinates | : | An ordered list of Cartesian points used by the coordinate index defined at the subtypes of IfcTessellatedFaceSet.
Closed | : | Indication whether the IfcTessellatedFaceSet is a closed shell or not. If omited no such information can be provided.

Inheritance Graph:

ENTITY IfcTessellatedFaceSet

| ENTITY IfcRepresentationItem

| INVERSE

LayerAssignment | : | SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems;
StyledByItem | : | SET [0:1] OF IfcStyledItem FOR Item;

| ENTITY IfcGeometricRepresentationItem

| ENTITY IfcTessellatedItem

| ENTITY IfcTessellatedFaceSet

Coordinates | : | IfcCartesianPointList3D;
Normals | : | OPTIONAL LIST [1:?] OF LIST [3:3] OF IfcStrippedOptional;
Closed | : | OPTIONAL IfcStrippedOptional;

| INVERSE

END_ENTITY;

Link to this page