IFC 4.3.x development IfcFacetedBrep Semantic definitions at the entity

The IfcFacetedBrep is a manifold solid brep with the restriction that all faces are planar and bounded polygons.


faceted brep instantiation
NOTE  Use of IfcFacetedBrep is restricted for boundary representation models with planar surfaces only. Those surfaces are implicitly represented by the bounding polygons. The diagram shows the topological and geometric representation items that are used for faceted breps.

Each IfcCartesianPoint, used within the IfcFacetedBrep shall be referenced three times by an IfcPolyLoop bounding a different IfcFace.

Figure 1 — Diagram showing the use of IfcFacetedBrep


NOTE  Definition according to ISO/CD 10303-42:1992
A faceted B-rep is a simple form of boundary representation model in which all faces are planar and all edges are straight lines. Unlike the B-rep model, edges and vertices are not represented explicitly in the model but are implicitly available through the poly loop entity. A faceted B-rep has to meet the same topological constraints as the manifold solid B-rep.

The faceted B-rep has been introduced in order to support the larger number of systems that allow boundary type solid representations with planar surfaces only.

NOTE  Entity adapted from manifold_solid_brep defined in ISO 10303-42.

HISTORY  New entity in IFC1.0


Informal Propositions:

  1. All the bounding loops of all the faces of all the shells in the IfcFacetedBrep shall be of type IfcPolyLoop.
  2. All vertices shall be referenced by all polyloops, sharing the vertex. I.e., each Cartesian point shall be references by at least three polyloops.

# Attribute Type Description
LayerAssignmentSET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment 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.
Dim INVALID The space dimensionality of this class, it is always 3.
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. Entity inheritance

dot_inheritance IfcFacetedBrepWithVoids IfcFacetedBrepWithVoids IfcFacetedBrep IfcFacetedBrep IfcFacetedBrepWithVoids->IfcFacetedBrep IfcManifoldSolidBrep IfcManifoldSolidBrep IfcFacetedBrep->IfcManifoldSolidBrep IfcAdvancedBrep IfcAdvancedBrep IfcAdvancedBrep->IfcManifoldSolidBrep IfcSolidModel IfcSolidModel IfcManifoldSolidBrep->IfcSolidModel IfcSolidModel_children 4 more... IfcSolidModel_children->IfcSolidModel IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcSolidModel->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem Formal representations

ENTITY IfcFacetedBrep
 SUBTYPE OF (IfcManifoldSolidBrep);