IFC 4.3.0.1 (IFC4X3) development

8.7.3.14 IfcLocalPlacement

8.7.3.14.1 Semantic definition

An IfcLocalPlacement defines the relative placement of a product in relation to the placement of another product or the absolute placement of a product within the geometric representation context of the project.

The IfcLocalPlacement allows that an IfcProduct can be placed by this IfcLocalPlacement (through the attribute_ObjectPlacement_) within the local coordinate system of the object placement of another IfcProduct, which is referenced by the PlacementRelTo. Rules to prevent cyclic relative placements have to be introduced on the application level.

If the PlacementRelTo is not given, then the IfcProduct is placed absolutely within the world coordinate system.

The following conventions shall apply as default relative positions if the relative placement is used. The conventions are given for all five direct subtypes of IfcProduct, the IfcSpatialStructureElement, IfcElement, IfcAnnotation, IfcGrid, IfcPort. More detailed placement information is given at the level of subtypes of those five types mentioned.

8.7.3.14.2 Entity inheritance

8.7.3.14.3 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.

Click to show 3 hidden inherited attributes Click to hide 3 inherited attributes
IfcLocalPlacement (1)
2 RelativePlacement IfcAxis2Placement

Geometric placement that defines the transformation from the related coordinate system into the relating. The placement can be either 2D or 3D, depending on the dimension count of the coordinate system.

Table 8.7.3.14.S

8.7.3.14.4 Formal propositions

Name Description
WR21

Ensures that a 3D local placement can only be relative (if exists) to a 3D parent local placement (and not to a 2D parent local placement).

IfcCorrectLocalPlacement(RelativePlacement, PlacementRelTo)
Table 8.7.3.14.T

8.7.3.14.5 Examples

8.7.3.14.6 Formal representation

ENTITY IfcLocalPlacement
 SUBTYPE OF (IfcObjectPlacement);
	RelativePlacement : IfcAxis2Placement;
 WHERE
	WR21 : IfcCorrectLocalPlacement(RelativePlacement, PlacementRelTo);
END_ENTITY;

8.7.3.14.7 References

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8.7.3.14.8 Changelog

  • attribute, PlacementRelTo