IFC 4.3.0.1 (IFC4X3) development

8.7.3.15 IfcObjectPlacement

ABSTRACT This definition may not be instantiated

8.7.3.15.1 Semantic definition

IfcObjectPlacement is an abstract supertype for the special types defining the object coordinate system. The IfcObjectPlacement has to be provided for each product that has a shape representation.

The object placement can be given:

  • absolute: by an axis2 placement, relative to the world coordinate system,
  • relative: by an axis2 placement, relative to the object placement of another product,
  • by grid reference: by the virtual intersection and reference direction given by two axes of a design grid,
  • linear placement: by distance along a curve, with possible offsets.

In any case the object placement has to unambiguously define the object coordinate system as either two-dimensional axis placement (IfcAxis2Placement2D) or three-dimensional axis placement (IfcAxis2Placement3D). The axis placement may have to be calculated.

8.7.3.15.2 Entity inheritance

8.7.3.15.3 Attributes

# Attribute Type Description
IfcObjectPlacement (3)
1 PlacementRelTo OPTIONAL IfcObjectPlacement

Reference to object placement that provides the relative placement with its placement in a grid, local coordinate system or linear referenced placement. If it is omitted, then in the case of linear placement it is established by the origin of horizontal alignment of the referenced IfcAlignment Axis. In the case of local placement it is established by the geometric representation context.

PlacesObject SET [0:?] OF IfcProduct FOR ObjectPlacement

The IfcObjectPlacement shall be used to provide a placement and an object coordinate system for instances of IfcProduct.

ReferencedByPlacements SET [0:?] OF IfcObjectPlacement FOR PlacementRelTo

No description available.

Table 8.7.3.15.A

8.7.3.15.4 Formal representation

ENTITY IfcObjectPlacement
 ABSTRACT SUPERTYPE OF (ONEOF
	(IfcGridPlacement
	,IfcLinearPlacement
	,IfcLocalPlacement));
	PlacementRelTo : OPTIONAL IfcObjectPlacement;
 INVERSE
	PlacesObject : SET [0:?] OF IfcProduct FOR ObjectPlacement;
	ReferencedByPlacements : SET [0:?] OF IfcObjectPlacement FOR PlacementRelTo;
END_ENTITY;

8.7.3.15.5 References

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8.7.3.15.6 Changelog

  • inverse attribute PlacesObject type, Changed from "SET OF [1:1] IfcProduct FOR ObjectPlacement" to "SET OF [0:?] IfcProduct FOR ObjectPlacement"
  • attribute, PlacementRelTo
  • inverse attribute, ReferencedByPlacements
  • inverse attribute, ReferencedByPlacements