The schema IfcGeometricConstraintResource defines the resources
used to determine the placement of the shape representation of a product within
the geometric representation context of a project. It also contains resource
definitions to be assigned to product connectivity definitions to determine the
connection geometry constraints between those products.
The primary application of this resource is to:
- determine the object placement used for the shape representation of
the object
- determine the constraints applied to the connectivity between two
shapes of objects
Placement
The placement of an product's shape is given by the
IfcObjectPlacement, refered to by the IfcProduct.ObjectPlacement.
The object placement defines the object coordinate system in which all shape
representations of that product are defined. It is given either as
- absolute placement
- relative placement
- placement relative to a grid
The absolute placement is specified by using IfcLocalPlacement
and omiting the PlacementRelTo attribute. The relative placement is
spefified by using IfcLocalPlacement and pointing the
PlacementRelTo attribute to an IfcObjectPlacement used in another
IfcProduct instance.
A placement relative to a grid is given by IfcGridPlacement
pointing to one (or two) virtual intersections of IfcGridAxis. If two
virtual intersections are references, than the second virtual intersections
specifies the orientation of the object placement.
Connection geometry
The connection geometry constrains the connectivity between the shapes
of two products. The constraint can be defined by geometric representation
items:
As a special type of surface representation, a constraint represented by
profile definitions may be defined. A profile constrained definition also
exists for the definition of a port or connectivity profile.
