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:

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 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.

	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.

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;