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IfcGridPlacement

Definition from IAI: 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.

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:

The direction of the y-axis of the object coordinate system is the orthogonal complement to the x-axis. The direction of the z-axis is the orientation of the cross product of the x-axis and the y-axis.

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.

without ref direction 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
with ref direction 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.

EXPRESS specification:

ENTITY IfcGridPlacement
SUBTYPE OF ( IfcObjectPlacement);
PlacementLocation  :  IfcVirtualGridIntersection;
PlacementRefDirection  :  OPTIONAL IfcVirtualGridIntersection;
END_ENTITY;

Attribute definitions:

PlacementLocation  :  A constraint on one or both ends of the path for an ExtrudedSolid.
PlacementRefDirection  :  Reference to a second grid axis intersection, which defines the orientation of the grid placement.

Inheritance graph

ENTITY IfcGridPlacement;
ENTITY IfcObjectPlacement;
INVERSE
PlacesObject  :  SET [1:1] OF IfcProduct FOR ObjectPlacement;
ReferencedByPlacements  :  SET OF IfcLocalPlacement FOR PlacementRelTo;
ENTITY IfcGridPlacement;
PlacementLocation  :  IfcVirtualGridIntersection;
PlacementRefDirection  :  OPTIONAL IfcVirtualGridIntersection;
END_ENTITY;