8.8.3.36 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:

Each face of the tessellated face set shall have:

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: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:attribute name="Normals" use="optional">
     <xs:simpleType>
      <xs:restriction>
       <xs:simpleType>
        <xs:list itemType="ifc:IfcParameterValue"/>
       </xs:simpleType>
       <xs:minLength value="3"/>
      </xs:restriction>
     </xs:simpleType>
    </xs:attribute>
    <xs:attribute name="Closed" type="xs:boolean" use="optional"/>
   </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 IfcParameterValue;
Closed : OPTIONAL BOOLEAN;
INVERSE
HasColours : SET [0:1] OF IfcIndexedColourMap FOR MappedTo;
HasTextures : SET [0:?] OF IfcIndexedTextureMap FOR MappedTo;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

Coordinates : An ordered list of Cartesian points used by the coordinate index defined at the subtypes of IfcTessellatedFaceSet.
Normals : An ordered list of directions used by the normal index defined at the subtypes of IfcTessellatedFaceSet. It is a two-dimensional list of directions provided by three parameter values.
Closed : Indication whether the IfcTessellatedFaceSet is a closed shell or not. If omited no such information can be provided.
HasColours : Reference to the indexed colour map providing the corresponding colour RGB values to the faces of the subtypes of IfcTessellatedFaceSet.
HasTextures : Reference to the indexed texture map providing the corresponding texture coordinates to the vertices bounding the faces of the subtypes of IfcTessellatedFaceSet.

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 IfcParameterValue;
Closed : OPTIONAL BOOLEAN;
INVERSE
HasColours : SET [0:1] OF IfcIndexedColourMap FOR MappedTo;
HasTextures : SET [0:?] OF IfcIndexedTextureMap FOR MappedTo;
END_ENTITY;

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