IFC (IFC4X3_ADD1) IfcAxis2PlacementLinear Semantic definition

The IfcAxis2PlacementLinear provides location and orientation to place items in a three-dimensional space confined to the context of a curve. Relative placement axes (Axis and RefDirection) are relative to the curve used for linear referencing provided in IfcPlacement Location (IfcPointByDistanceExpression BasisCurve), maintaining the relationship to the tangent of the curve. 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.

IfcPlacement (2)
1 Location IfcPoint

The geometric position of a reference point, such as the center of a circle, of the item to be located.

* Dim IfcDimensionCount

This attribute is formally derived.


The space dimensionality of this class, derived from the dimensionality of the location.

Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes
IfcAxis2PlacementLinear (2)
2 Axis OPTIONAL IfcDirection

The exact direction of the local Z Axis.

3 RefDirection OPTIONAL IfcDirection

The direction used to determine the direction of the local X Axis. In case both Axis and RefDirection are set and not perpendicular an adjustment is necessary to maintain orthogonality to the Axis direction. If RefDirection is omitted, the direction is taken from the curve tangent at Location.

Table Formal propositions

Name Description

The Location on parent type IfcPlacement shall be of type IfcPointByDistanceExpression


The Axis and RefDirection shall not be parallel or anti-parallel.

(NOT (EXISTS (Axis))) OR (NOT (EXISTS (RefDirection))) OR (IfcCrossProduct(Axis,RefDirection).Magnitude > 0.0)
Table Examples Formal representation

ENTITY IfcAxis2PlacementLinear
 SUBTYPE OF (IfcPlacement);
	Axis : OPTIONAL IfcDirection;
	RefDirection : OPTIONAL IfcDirection;
	WR2 : (NOT (EXISTS (Axis))) OR (NOT (EXISTS (RefDirection))) OR (IfcCrossProduct(Axis,RefDirection).Magnitude > 0.0);
END_ENTITY; Changelog IFC4.3_ADD1

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