Boundary Representation  NURBS  
Advanced Brep  
Représentation frontière avancée 
Item  SPF  XML  Change  Description 

4.0.0.0  
IfcAdvancedBrep  ADDED 
An advanced Brep is a boundary representation model in which all faces, edges and vertices are explicitly represented. It is a solid with explicit topology and elementary or freeform geometry. The faces of the Brep are of type IfcAdvancedFace. An advanced Brep has to meet the same topological constraints as the manifold solid Brep.
NOTE The advanced Brep has been introduced in order to support the increasing number of applications that can define and exchange Brep models based on NURBS or other bspline surfaces.
Figure 347 illustrates use of IfcAdvancedBrep for boundary representation models with bspline surfaces. The diagram shows the topological and geometric representation items that are used for advanced Breps, based on IfcAdvancedFace. 

Figure 347 — Advanced Brep, bspline surface


Figure 348 illustrates use of IfcAdvancedBrep for boundary representation models with elementary surfaces. The diagram shows the topological and geometric representation items that are used for advanced Breps, based on IfcAdvancedFace. It shows the use of IfcIntersectionCurve to provide the geometric representation of the edge curve both as 3D curve and as u,v pcurve in the parametric space of the adjacent surfaces. 

Figure 348 — Advanced Brep, elementary surface 
NOTE Entity adapted from advanced_brep_shape_representation defined in ISO 10303514.
HISTORY New entity in IFC4
Informal Propositions:
Rule  Description 

HasAdvancedFaces  Each face of the advanced Brep shall be of type IfcAdvancedFace. 
#  Attribute  Type  Cardinality  Description  G 

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  
IfcGeometricRepresentationItem  
IfcSolidModel  
Dim :=3  IfcDimensionCount  The space dimensionality of this class, it is always 3.  X  
IfcManifoldSolidBrep  
1  Outer  IfcClosedShell  A closed shell defining the exterior boundary of the solid. The shell normal shall point away from the interior of the solid.  X  
IfcAdvancedBrep 
<xs:element name="IfcAdvancedBrep" type="ifc:IfcAdvancedBrep" substitutionGroup="ifc:IfcManifoldSolidBrep" nillable="true"/>
<xs:complexType name="IfcAdvancedBrep">
<xs:complexContent>
<xs:extension base="ifc:IfcManifoldSolidBrep"/>
</xs:complexContent>
</xs:complexType>
ENTITY IfcAdvancedBrep
SUPERTYPE OF(IfcAdvancedBrepWithVoids)
SUBTYPE OF (IfcManifoldSolidBrep);
WHERE
HasAdvancedFaces : SIZEOF(QUERY(Afs <* SELF\IfcManifoldSolidBrep.Outer.CfsFaces 
(NOT ('IFCTOPOLOGYRESOURCE.IfcAdvancedFace' IN TYPEOF(Afs)))
)) = 0;
END_ENTITY;