IfcGridPlacement

Semantic definitions at the entity

Entity definition

The IfcGridPlacement provides a specialization of IfcObjectPlacement in which the placement and axis direction of the object coordinate system is defined by a reference to the design grid as defined in IfcGrid.

The location of the object coordinate system is given by the attribute PlacementLocation. The axis direction (of x-axis) of the object coordinate system is given:

by the tangent of the first grid axis (PlacementLocation.IntersectingAxes[1]) at the virtual intersection (maybe using the offset curve, if PlacementLocation.OffsetDistances is given) in case that the PlacementRefDirection is not given,
by the tangent between the virtual grid intersection of PlacementLocation and the virtual grid intersection of PlacementRefDirection in case that the PlacementRefDirection is given.

The direction of the y-axis of the IfcGridPlacement is the orthogonal complement to the x-axis. The plane defined by the x and y axis shall be co-planar to the xy plane of the local placement of the IfcGrid.

NOTE The PlacementLocation.OffsetDistances[3] and the PlacementRefDirection.OffsetDistances[3] shall either not be assigned or should have the same z offset value.

The direction of the z-axis is the orientation of the cross product of the x-axis and the y-axis, i.e. the z-axis of the IfcGridPlacement shall be co-linear to the z-axis of the local placement of the IfcGrid.

HISTORY New entity in IFC Release 1.5. The entity name was changed from IfcConstrainedPlacement. in IFC Release 2x.

Geometry use definitions:

The following example shows the usage of placement location and direction for an IfcGridPlacement.

	PlacementRefDirection is not given - the object coordinate system is defined by: its location: given by the virtual grid intersection of PlacementLocation its x-axis direction: given by the tangent of the first intersecting axis in the offset location of the virtual grid intersection
	PlacementRefDirection is given - the object coordinate system is defined by: its location: given by the virtual grid intersection of PlacementLocation its x-axis direction: given by the tangent of the line between the virtual grid intersection of the PlacementLocation and the virtual grid intersection of the PlacementRefDirection.

Attribute definitions

#	Attribute	Type	Cardinality	Description	A
1	PlacementLocation	IfcVirtualGridIntersection	[1:1]	A constraint on one or both ends of the path for an ExtrudedSolid.	X
2	PlacementRefDirection	IfcVirtualGridIntersection	[0:1]	Reference to a second grid axis intersection, which defines the orientation of the grid placement.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	A
IfcObjectPlacement
	PlacesObject	IfcProduct @ObjectPlacement	S[1:1]	The IfcObjectPlacement shall be used to provide a placement and an object coordinate system for a single instance of IfcProduct.
	ReferencedByPlacements	IfcLocalPlacement @PlacementRelTo	S[0:?]	Placements that are given relative to this placement of an object.
IfcGridPlacement
1	PlacementLocation	IfcVirtualGridIntersection	[1:1]	A constraint on one or both ends of the path for an ExtrudedSolid.	X
2	PlacementRefDirection	IfcVirtualGridIntersection	[0:1]	Reference to a second grid axis intersection, which defines the orientation of the grid placement.	X

Formal representations

XSD Specification

 <xs:element name="IfcGridPlacement" type="ifc:IfcGridPlacement" substitutionGroup="ifc:IfcObjectPlacement" nillable="true"/>

 <xs:complexType name="IfcGridPlacement">

  <xs:complexContent>

   <xs:extension base="ifc:IfcObjectPlacement">

    <xs:sequence>

     <xs:element name="PlacementLocation" type="ifc:IfcVirtualGridIntersection" nillable="true"/>

     <xs:element name="PlacementRefDirection" type="ifc:IfcVirtualGridIntersection" nillable="true" minOccurs="0"/>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcGridPlacement

 SUBTYPE OF (IfcObjectPlacement);

  PlacementLocation : IfcVirtualGridIntersection;

  PlacementRefDirection : OPTIONAL IfcVirtualGridIntersection;

END_ENTITY;

 EXPRESS-G diagram