8.20.3.13 IfcOrientedEdge

8.20.3.13.1 Semantic definition

The IfcOrientedEdge represents an IfcEdge with an Orientation flag applied. It allows to reuse the same IfcEdge when traversed exactly twice, once forwards and once backwards.

The reused edge with a geometric representation as IfcEdgeCurve defines the edge in 3D coordinate space. In some cases, particularly when using elementary or swept surfaces, there is the risk of imprecise mapping of the 3D (x, y, z) IfcEdgeCurve onto the adjacent surfaces to determine the boundaries of these surfaces. The optional CurveOnSurface defines the 2D (u, v) edge within the parametric space of the surface. It could be used to determine the correctness of the mapping of the 3D IfcEdgeCurve onto this surface.

example — Figure 8.20.3.13.A — Curve on surface representation of an

A common practice is solid modelling systems is to have an entity that represents the "use" or "traversal" of an edge. This "use" entity explicitly represents the requirement in a manifold solid that each edge must be traversed exactly twice, once in each direction. The "use" functionality is provided by the edge subtype oriented edge.

8.20.3.13.2 Entity inheritance

8.20.3.13.3 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.
IfcEdge (2)
1	EdgeStart	IfcVertex	Start point (vertex) of the edge.
2	EdgeEnd	IfcVertex	End point (vertex) of the edge. The same vertex can be used for both EdgeStart and EdgeEnd.
Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes
IfcOrientedEdge (4)
3	EdgeElement	IfcEdge	Edge entity used to construct this oriented edge.
4	Orientation	IfcBoolean	BOOLEAN, If TRUE the topological orientation as used coincides with the orientation from start vertex to end vertex of the edge element. If FALSE otherwise.
1*	EdgeStart	IfcVertex	This attribute is formally derived. `IfcBooleanChoose (Orientation, EdgeElement.EdgeStart, EdgeElement.EdgeEnd)` The start vertex of the oriented edge. It derives from the vertices of the edge element after taking account of the orientation.
2*	EdgeEnd	IfcVertex	This attribute is formally derived. `IfcBooleanChoose (Orientation, EdgeElement.EdgeEnd, EdgeElement.EdgeStart)` The end vertex of the oriented edge. It derives from the vertices of the edge element after taking account of the orientation.

Table 8.20.3.13.D

8.20.3.13.4 Formal propositions

Name	Description
EdgeElementNotOriented	The edge element shall not be an oriented edge.
`NOT('IFC4X3_DEV_040635d1.IFCORIENTEDEDGE' IN TYPEOF(EdgeElement))`

Table 8.20.3.13.E

8.20.3.13.5 Examples

Figure 8.20.3.13.B

Basin Advanced Brep
Figure 8.20.3.13.C

Cube Advanced Brep

8.20.3.13.6 Formal representation

ENTITY IfcOrientedEdge
 SUBTYPE OF (IfcEdge);
	EdgeElement : IfcEdge;
	Orientation : IfcBoolean;
 DERIVE
	 SELF\IfcEdge.EdgeStart : IfcVertex := IfcBooleanChoose 
(Orientation, EdgeElement.EdgeStart, EdgeElement.EdgeEnd);
	 SELF\IfcEdge.EdgeEnd : IfcVertex := IfcBooleanChoose 
(Orientation, EdgeElement.EdgeEnd, EdgeElement.EdgeStart);
 WHERE
	EdgeElementNotOriented : NOT('IFC4X3_DEV_040635d1.IFCORIENTEDEDGE' IN TYPEOF(EdgeElement));
END_ENTITY;