IFC (IFC4X3_ADD2) official IfcPolyLoop Semantic definition

A poly loop shall conform to the following topological constraints: > * the loop has the genus of one. * the following equation shall be satisfied Image

The IfcPolyLoop is always closed and the last segment is from the last IfcCartesianPoint in the list of Polygon's to the first IfcCartesianPoint. Therefore the first point shall not be repeated at the end of the list, neither by referencing the same instance, nor by using an additional instance of IfcCartesianPoint having the coordinates as the first point.

Informal Propositions

  1. All the points in the polygon defining the poly loop shall be coplanar.
  2. The first and the last Polygon shall be different by value. Entity inheritance 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.

Click to show 2 hidden inherited attributes Click to hide 2 inherited attributes
IfcPolyLoop (1)
1 Polygon LIST [3:?] OF UNIQUE IfcCartesianPoint

List of points defining the loop. There are no repeated points in the list.

Table Formal propositions

Name Description

The space dimensionality of all Points shall be the same.

SIZEOF(QUERY(Temp <* Polygon | Temp.Dim <> Polygon[1].Dim)) = 0
Table Examples Formal representation

ENTITY IfcPolyLoop
 SUBTYPE OF (IfcLoop);
	Polygon : LIST [3:?] OF UNIQUE IfcCartesianPoint;
	AllPointsSameDim : SIZEOF(QUERY(Temp <* Polygon | Temp.Dim <> Polygon[1].Dim)) = 0;
END_ENTITY; References

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Is this page difficult to understand? Let us know! Changelog IFC4

  • where rule, AllPointsSameDim
  • where rule, WR21 IFC4.2 IFC4.3_ADD2