The presentation layer assignment provides the layer name (and optionally a description and an identifier) for a collection of geometric representation items. The IfcPresentationLayerAssignment corresponds to the term "CAD Layer" and is used mainly for grouping and visibility control.
Visibility and access control and layer style assignment (colour, line style, line width) is handled by the subtype IfcPresentationLayerAssignmentWithStyle.
Attribute use definition
Figure 188.8.131.52.A illustrates assignment of items by shape representation or representation item. The set of AssignedItems can either include a whole shape representation, or individual geometric representation items. If both, the IfcShapeRepresentation has a layer assignment, and an individual geometric representation item in the set of IfcShapeRepresentation.Items, then the layer assignment of the IfcGeometricRepresentationItem overrides the layer assignment of the IfcShapeRepresentation.
Name of the layer.
Additional description of the layer.
|3||AssignedItems||SET [1:?] OF IfcLayeredItem||
The set of layered items, which are assigned to this layer.
An (internal) identifier assigned to the layer.
The items within the set of AssignedItems that can be assigned to a presentation layer shall be geometric shape representation or representation items.
ENTITY IfcPresentationLayerAssignment SUPERTYPE OF (ONEOF (IfcPresentationLayerWithStyle)); Name : IfcLabel; Description : OPTIONAL IfcText; AssignedItems : SET [1:?] OF IfcLayeredItem; Identifier : OPTIONAL IfcIdentifier; WHERE ApplicableItems : SIZEOF(QUERY(temp <* AssignedItems | ( SIZEOF(TYPEOF(temp) * [ 'IFC4X3_DEV_9f90c1f0.IFCSHAPEREPRESENTATION', 'IFC4X3_DEV_9f90c1f0.IFCGEOMETRICREPRESENTATIONITEM', 'IFC4X3_DEV_9f90c1f0.IFCMAPPEDITEM']) = 1) )) = SIZEOF(AssignedItems); END_ENTITY;