8.8.3.1 IfcAdvancedBrep
8.8.3.1.1 Semantic definition
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.
Figure 8.8.3.1.A 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 8.8.3.1.B 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.
Informal Propositions:
 each face is a face surface;
 each face surface has its geometry defined by an elementary surface, swept surface or a bspline surface;
 the edges used to define the boundaries of the face shall all reference an edge curve
 each curve used to define the geometry of the faces and face bounds shall be either a conic, or a line or a polyline or a bspline curve
 the edges used to define the face boundaries shall all be trimmed by vertices of type vertex point
 no loop used to define a face bound shall be of the oriented subtype
8.8.3.1.2 Entity inheritance

 IfcSolidModel
 IfcAnnotationFillArea
 IfcBooleanResult
 IfcBoundingBox
 IfcCartesianPointList
 IfcCartesianTransformationOperator
 IfcCsgPrimitive3D
 IfcCurve
 IfcDirection
 IfcFaceBasedSurfaceModel
 IfcFillAreaStyleHatching
 IfcFillAreaStyleTiles
 IfcGeometricSet
 IfcHalfSpaceSolid
 IfcLightSource
 IfcPlacement
 IfcPlanarExtent
 IfcPoint
 IfcSectionedSpine
 IfcSegment
 IfcShellBasedSurfaceModel
 IfcSurface
 IfcTessellatedItem
 IfcTextLiteral
 IfcVector
8.8.3.1.3 Attributes
#  Attribute  Type  Description 

IfcRepresentationItem (2)  
LayerAssignment  SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems 
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. 

StyledByItem  SET [0:1] OF IfcStyledItem FOR Item 
Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve. 

IfcSolidModel (1)  
*  Dim  IfcDimensionCount 
This attribute is formally derived.
The space dimensionality of this class, it is always 3. 
Click to show 3 hidden inherited attributes Click to hide 3 inherited attributes  
IfcManifoldSolidBrep (1)  
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. 
8.8.3.1.4 Formal propositions
Name  Description 

HasAdvancedFaces 
Each face of the advanced Brep shall be of type IfcAdvancedFace. 

8.8.3.1.5 Formal representation
ENTITY IfcAdvancedBrep
SUPERTYPE OF (ONEOF
(IfcAdvancedBrepWithVoids))
SUBTYPE OF (IfcManifoldSolidBrep);
WHERE
HasAdvancedFaces : SIZEOF(QUERY(Afs <* SELF\IfcManifoldSolidBrep.Outer.CfsFaces 
(NOT ('IFC4X3_DEV_9f90c1f0.IFCADVANCEDFACE' IN TYPEOF(Afs)))
)) = 0;
END_ENTITY;