8.20.3.1 IfcAdvancedFace

8.20.3.1.1 Semantic definition

An advanced face is a specialization of a face surface that has to meet requirements on using particular topological and geometric representation items for the definition of the faces, edges and vertices.

An IfcAdvancedFace is restricted to:

have a face surface geometry of type IfcElementarySurface, IfcSweptSurface or IfcBSplineSurface,
have one IfcFaceOuterBound as the bound of the face, with the exception of closed surfaces,
have all faces to be bound by IfcEdgeLoop or IfcVertexLoop,
have all edges to have an edge curve geometry,
have the edge curve geometry restricted to IfcLine, IfcConic, IfcPolyline, or IfcBSplineCurve

In case of closed faces with periodic surfaces, such as cylindrical or spherical surfaces, the following applies:

the edges of the closed surface, in case of a cylindrical surface the upper and lower cap, refer to the same instance of IfcVertexPoint twice,
no IfcFaceOuterBound is provided, or the IfcFaceOuterBound is constructed using an IfcSeamCurve at the periodic end of the underlying closed surface, in case of a cylindrical surface at 0./360. degree.

cylindrical surface — Figure 8.20.3.1.A — Use of _IfcCylindricalSurface_ as underlying surface of an _IfcAdvancedFace_

8.20.3.1.2 Entity inheritance

8.20.3.1.3 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. 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.
	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. IFC2x3-CHANGE The inverse attribute StyledByItem has been added.
IfcFace (2)
1	Bounds	SET [1:?] OF IfcFaceBound	Boundaries of the face.
	HasTextureMaps	SET [0:?] OF IfcTextureMap FOR MappedTo	No description available.
Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes
IfcFaceSurface (2)
2	FaceSurface	IfcSurface	The surface which defines the internal shape of the face. This surface may be unbounded. The domain of the face is defined by this surface and the bounding loops in the inherited attribute SELF\FaceBounds.
3	SameSense	IfcBoolean	This flag indicates whether the sense of the surface normal agrees with (TRUE), or opposes (FALSE), the sense of the topological normal to the face.

Table 8.20.3.1.B

8.20.3.1.4 Formal propositions

Name	Description
ApplicableEdgeCurves	The types of curve used to define the geometry of edges shall be restricted to IfcLine, IfcConic, IfcPolyline, or IfcBSplineCurve.
`SIZEOF(QUERY (ElpFbnds <* QUERY (Bnds <* SELF\IfcFace.Bounds \| 'IFC4X3.IFCEDGELOOP' IN TYPEOF(Bnds.Bound)) \| NOT (SIZEOF (QUERY (Oe <* ElpFbnds.Bound\IfcEdgeLoop.EdgeList \| NOT (SIZEOF (['IFC4X3.IFCLINE', 'IFC4X3.IFCCONIC', 'IFC4X3.IFCPOLYLINE', 'IFC4X3.IFCBSPLINECURVE'] * TYPEOF(Oe\IfcOrientedEdge.EdgeElement\IfcEdgeCurve.EdgeGeometry)) = 1 ) )) = 0 ))) = 0`
ApplicableSurface	The geometry used in the definition of the face shall be restricted. The face geometry shall be an IfcElementarySurface, IfcSweptSurface, or IfcBSplineSurface.
`SIZEOF ( ['IFC4X3.IFCELEMENTARYSURFACE', 'IFC4X3.IFCSWEPTSURFACE', 'IFC4X3.IFCBSPLINESURFACE'] * TYPEOF(SELF\IfcFaceSurface.FaceSurface)) = 1`
RequiresEdgeCurve	The geometry of all bounding edges of the face shall be fully defined as IfcEdgeCurve's.
`SIZEOF(QUERY (ElpFbnds <* QUERY (Bnds <* SELF\IfcFace.Bounds \| 'IFC4X3.IFCEDGELOOP' IN TYPEOF(Bnds.Bound)) \| NOT (SIZEOF (QUERY (Oe <* ElpFbnds.Bound\IfcEdgeLoop.EdgeList \| NOT('IFC4X3.IFCEDGECURVE' IN TYPEOF(Oe\IfcOrientedEdge.EdgeElement) ))) = 0 ))) = 0`

Table 8.20.3.1.C

8.20.3.1.5 Formal representation

ENTITY IfcAdvancedFace
 SUBTYPE OF (IfcFaceSurface);
 WHERE
	ApplicableEdgeCurves : SIZEOF(QUERY (ElpFbnds <* 
  QUERY (Bnds <* SELF\IfcFace.Bounds |
    'IFC4X3.IFCEDGELOOP' IN TYPEOF(Bnds.Bound)) |
     NOT (SIZEOF (QUERY (Oe <* ElpFbnds.Bound\IfcEdgeLoop.EdgeList |
       NOT (SIZEOF (['IFC4X3.IFCLINE',
                     'IFC4X3.IFCCONIC',
                     'IFC4X3.IFCPOLYLINE',
                     'IFC4X3.IFCBSPLINECURVE'] *
         TYPEOF(Oe\IfcOrientedEdge.EdgeElement\IfcEdgeCurve.EdgeGeometry)) = 1 )
  )) = 0
))) = 0;
	ApplicableSurface : SIZEOF (
['IFC4X3.IFCELEMENTARYSURFACE',
 'IFC4X3.IFCSWEPTSURFACE',
 'IFC4X3.IFCBSPLINESURFACE'] *
TYPEOF(SELF\IfcFaceSurface.FaceSurface)) = 1;
	RequiresEdgeCurve : SIZEOF(QUERY (ElpFbnds <* 
  QUERY (Bnds <* SELF\IfcFace.Bounds |
    'IFC4X3.IFCEDGELOOP' IN TYPEOF(Bnds.Bound)) |
     NOT (SIZEOF (QUERY (Oe <* ElpFbnds.Bound\IfcEdgeLoop.EdgeList |
       NOT('IFC4X3.IFCEDGECURVE' IN 
       TYPEOF(Oe\IfcOrientedEdge.EdgeElement)
  ))) = 0
))) = 0;
END_ENTITY;

8.20.3.1.6 References

IfcFaceSurface