The projection element is a
specialization of the general feature element to represent
projections applied to building elements. It represents a solid
attached to any element that has physical manifestation.
EXAMPLE A wall projection such as a pilaster strip is handled by
NOTE View definitions or implementer agreements
may restrict the types of elements to which
IfcProjectionElement can be applied.
An IfcProjectionElement has to be linked to a element
(all subtypes of IfcElement) by using the
IfcRelProjectsElement relationship. Its existence depends on
the existence of the master element. The relationship implies a
Boolean union operation between the volume of the projection
element and the volume of the element.
HISTORY New entity in IFC2x2.
IFC4 CHANGE The attribute PredefinedType has been added at the end of attribute list.
Containment Use Definition
The IfcProjectionElement shall not participate in the
containment relationship, i.e. it is not linked directly to the
spatial structure of the project. It has a mandatory
ProjectsElements inverse relationship pointing to the
IfcElement that is contained in the spatial structure.
- The inverse relationship ContainedInStructure shall be
Common Use Definitions
The following concepts are inherited at supertypes:
Property Sets for Objects
The Property Sets for Objects concept applies to this entity as shown in Table 60.
Table 60 — IfcProjectionElement Property Sets for Objects
The Quantity Sets concept applies to this entity as shown in Table 61.
Table 61 — IfcProjectionElement Quantity Sets
The Product Placement concept applies to this entity as shown in Table 62.
Table 62 — IfcProjectionElement Product Placement
The local placement for IfcOpeningRecess is defined in
its supertype IfcProduct. It is defined by the
IfcLocalPlacement, which defines the local coordinate system
that is referenced by all geometric representations.
- The PlacementRelTo relationship of
IfcLocalPlacement should point to the local placement of the
same element, to which the projection adds, i.e. referred to by
The Body Geometry concept applies to this entity as shown in Table 63.
Table 63 — IfcProjectionElement Body Geometry
The geometric representation of IfcProjectionElement is
defined using the swept area solid geometry. The following
attribute values for the IfcShapeRepresentation holding this
geometric representation shall be used:
- RepresentationIdentifier : 'Body'
- RepresentationType : 'SweptSolid'
The following additional constraints apply to the swept solid
As shown in Figure 129, the following interpretation of dimension parameter applies for
- IfcRectangleProfileDef.YDim interpreted as projection
- IfcRectangleProfileDef.XDim interpreted as projection
- IfcExtrudedAreaSolid.Depth is interpreted as projection
NOTE Rectangles are now defined centric, the placement location has to be set:
NOTE The local placement directions for the IfcProjectionElement are only given as an example, other directions are valid as well.
Figure 129 — Projection representation
The general b-rep geometric representation of
IfcProjectionElement is defined using the Brep geometry. The
Brep representation allows for the representation of complex
element shape. The following attribute values for the
IfcShapeRepresentation holding this geometric representation
shall be used:
- RepresentationIdentifier : 'Body'
- RepresentationType : 'Brep'
XSD Specification: <xs:element name="IfcProjectionElement" type="ifc:IfcProjectionElement" substitutionGroup="ifc:IfcFeatureElementAddition" nillable="true"/>
<xs:attribute name="PredefinedType" type="ifc:IfcProjectionElementTypeEnum" use="optional"/>
|PredefinedType|| : ||
Predefined generic type for a projection element that is specified in an enumeration. There may be a property set given specificly for the predefined types.
IFC4 CHANGE The attribute has been added at the end of the entity definition.
Link to this page