IfcAdvancedBrep

Item	SPF	XML	Change	Description
IFC2x3 to IFC4 4.0.0.0
IfcAdvancedBrep			ADDED

Semantic definitions at the entity

Entity definition

An advanced B-rep 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 free-form geometry. The faces of the B-rep are of type IfcAdvancedFace. An advanced B-rep has to meet the same topological constraints as the manifold solid B-rep.

NOTE The advanced B-rep has been introduced in order to support the increasing number of applications that can define and exchange B-rep models based on NURBS or other b-spline surfaces.

	Figure 471 illustrates use of IfcAdvancedBrep for boundary representation models with b-spline surfaces. The diagram shows the topological and geometric representation items that are used for advanced B-reps, based on IfcAdvancedFace.
Figure 471 — Advanced Brep, b-spline surface
	Figure 472 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 B-reps, 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 472 — Advanced Brep, elementary surface

NOTE Entity adapted from advanced_brep_shape_representation defined in ISO 10303-514.

HISTORY New entity in IFC4

Informal Propositions:

each face is a face surface;
each face surface has its geometry defined by an elementary surface, swept surface or a b-spline 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 b-spline 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

Formal Propositions

Rule	Description
HasAdvancedFaces	Each face of the advanced B-rep shall be of type IfcAdvancedFace.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	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

Formal representations

XML Specification

 <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>

EXPRESS Specification


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;

 EXPRESS-G diagram

	Boundary Representation - NURBS
	Advanced Brep
	Représentation frontière avancée