IfcShapeRepresentation

Semantic definitions at the entity

Entity definition

The IfcShapeRepresentation represents the concept of a particular geometric representation of a product or a product component within a specific geometric representation context. The inherited attribute RepresentationType is used to define the geometric model used for the shape representation (e.g. 'SweptSolid', or 'Brep'), the inherited attribute RepresentationIdentifier is used to denote the kind of the representation captured by the IfcShapeRepresentation (e.g. 'Axis', 'Body', etc.).

Several representation identifiers for shape representation are included as predefined values for RepresentationIdentifier. Table 775 indicates the defined list of values for RepresentationIdentifier.

Identifier
CoG	Point to identify the center of gravity of an element. This value can be used for validation purposes.
Box	Bounding box as simplified 3D box geometry of an element
Annotation	3D annotations not representing elements
Axis	2D or 3D Axis, or single line, representation of an element
FootPrint	2D Foot print, or double line, representation of an element, projected to ground view
Profile	3D line representation of a profile being planar, e.g. used for door and window outlines
Surface	3D Surface representation, e.g. of an analytical surface, of an elementplane)
Reference	3D representation that is not part of the Body representation. This is used, e.g., for opening geometries, if there are to be excluded from an implicit Boolean operation.
Body	3D Body representation, e.g. as wireframe, surface, or solid model, of an element
Body-FallBack	3D Body representation, e.g. as tessellation, or other surface, or boundary representation, added in addition to the solid model (potentially involving Boolean operations) of an element
Clearance	3D clearance volume of the element. Such clearance region indicates space that should not intersect with the 'Body' representation of other elements, though may intersect with the 'Clearance' representation of other elements.
Lighting	Representation of emitting light as a light source within a shape representation

Table 775 — Representation identifiers

Several representation types for shape representation are included as predefined values for RepresentationType. Table 776 indicates the defined list of values for RepresentationType.

Type
Point		2 or 3 dimensional point(s)
PointCloud		3 dimensional points prepresented by a point list
Segment		2 or 3 dimensional segment(s)
Curve		2 or 3 dimensional curve(s)
	Curve2D	2 dimensional curve(s)
	Curve3D	3 dimensional curve(s)
Surface		2 or 3 dimensional surface(s)
	Surface2D	2 dimensional surface(s) (a region on ground view)
	Surface3D	3 dimensional surface(s)
	SectionedSurface	swept surface(s) created by sweeping open profiles along a directrix
FillArea		2D region(s) represented as a filled area (hatching)
Text		text defined as text literals
AdvancedSurface		3 dimensional b-spline surface(s)
GeometricSet		points, curves, surfaces (2 or 3 dimensional)
	GeometricCurveSet	points, curves (2 or 3 dimensional)
	Annotation2D	points, curves (2 or 3 dimensional), hatches and text (2 dimensional)
SurfaceModel		face based and shell based surface model(s), or tessellated surface model(s)
	Tessellation	tessellated surface representation(s) only
SolidModel		including swept solid, Boolean results and Brep bodies; more specific types are:
	SweptSolid	swept area solids, by extrusion and revolution, excluding tapered sweeps
	AdvancedSweptSolid	swept area solids created by sweeping a profile along a directrix, and tapered sweeps
	Brep	faceted Brep's with and without voids
	AdvancedBrep	Brep's based on advanced faces, with b-spline surface geometry, with and without voids
	CSG	Boolean results of operations between solid models, half spaces and Boolean results
	Clipping	Boolean differences between swept area solids, half spaces and Boolean results
	Voxel	Voxel grid(s)
additional types		some additional representation types are provided:
	BoundingBox	simplistic 3D representation by a bounding box
	SectionedSpine	cross section based representation of a spine curve and planar cross sections. It can represent a surface or a solid and the interpolations of the between the cross sections is not defined
	LightSource	light source with (depending on type) position, orientation, light colour, intensity and attenuation
	MappedRepresentation	representation based on mapped item(s), referring to a representation map. Note: it can be seen as an inserted block reference. The shape representation of the mapped item has a representation type declaring the type of its representation items.

Table 776 — Representation types

NOTE The definition relates to shape_representation defined in ISO 10303-41.

HISTORY New entity in IFC1.5.

IFC4 CHANGE The RepresentationType's 'Point', 'PointCloud', 'Curve', 'Curve3D', 'Surface', 'Surface2D', 'Surface3D', 'FillArea', 'Text', 'Tessellation', 'AdvancedBrep', 'LightSource', and the RepresentationIdentifier 'Body-FallBack', 'Profile', 'Clearance', 'Lighting' have been added.

Formal Propositions

Rule	Description
CorrectContext	The context to which the IfcShapeRepresentation is assign, shall be of type IfcGeometricRepresentationContext.
NoTopologicalItem	No topological representation item shall be directly used for shape representations, with the exception of IfcVertexPoint, IfcEdgeCurve, IfcFaceSurface.
HasRepresentationType	A representation type should be provided for the shape representation.
HasRepresentationIdentifier	A representation identifier should be provided for the shape representation.
CorrectItemsForType	Checks the proper use of Items according to the RepresentationType.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
IfcRepresentation
1	ContextOfItems	IfcRepresentationContext		Definition of the representation context for which the different subtypes of representation are valid.	X
2	RepresentationIdentifier	IfcLabel	?	The optional identifier of the representation as used within a project.	X
3	RepresentationType	IfcLabel	?	The description of the type of a representation context. The representation type defines the type of geometry or topology used for representing the product representation. More information is given at the subtypes IfcShapeRepresentation and IfcTopologyRepresentation. The supported values for context type are to be specified by implementers agreements.	X
4	Items	IfcRepresentationItem	S[1:?]	Set of geometric representation items that are defined for this representation.	X
	RepresentationMap	IfcRepresentationMap @MappedRepresentation	S[0:1]	Use of the representation within an IfcRepresentationMap. If used, this IfcRepresentation may be assigned to many representations as one of its Items using an IfcMappedItem. Using IfcRepresentationMap is the way to share one representation (often of type IfcShapeRepresentation) by many products. IFC2x3 CHANGE The inverse attribute LayerAssignments has been added	X
	LayerAssignments	IfcPresentationLayerAssignment @AssignedItems	S[0:?]	Assignment of the whole representation to a single or multiple layer(s). The LayerAssigments can be overridden by LayerAssigments of the IfcRepresentationItem's within the list of Items. NOTE Implementation agreements can restrict the maximum number of layer assignments to 1. IFC2x3 CHANGE The inverse attribute LayerAssignments has been added	X
	OfProductRepresentation	IfcProductRepresentation @Representations	S[0:?]	Reference to the product representations to which this individual representation applies. In most cases it is the reference to one or many product shapes, to which this shape representation is applicable. IFC4 CHANGE Inverse relationship cardinality relaxed to be 0:N.	X
IfcShapeModel
	OfShapeAspect	IfcShapeAspect @ShapeRepresentations	S[0:1]	Reference to the shape aspect, for which it is the shape representation.	X
IfcShapeRepresentation

Formal representations

XML Specification

 <xs:element name="IfcShapeRepresentation" type="ifc:IfcShapeRepresentation" substitutionGroup="ifc:IfcShapeModel" nillable="true"/>

 <xs:complexType name="IfcShapeRepresentation">

  <xs:complexContent>

   <xs:extension base="ifc:IfcShapeModel"/>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcShapeRepresentation

 SUBTYPE OF (IfcShapeModel);

 WHERE

  CorrectContext : 'IFCREPRESENTATIONRESOURCE.IfcGeometricRepresentationContext' 

IN TYPEOF(SELF\IfcRepresentation.ContextOfItems);
  NoTopologicalItem : SIZEOF(QUERY(temp <* Items | 

  ('IFCTOPOLOGYRESOURCE.IfcTopologicalRepresentationItem' IN TYPEOF(temp))

    AND (NOT(SIZEOF(

      ['IFCTOPOLOGYRESOURCE.IfcVertexPoint',

       'IFCTOPOLOGYRESOURCE.IfcEdgeCurve',

       'IFCTOPOLOGYRESOURCE.IfcFaceSurface'] * TYPEOF(temp)) = 1))

)) = 0;
  HasRepresentationType : EXISTS(SELF\IfcRepresentation.RepresentationType);
  HasRepresentationIdentifier : EXISTS(SELF\IfcRepresentation.RepresentationIdentifier);
  CorrectItemsForType : IfcShapeRepresentationTypes(SELF\IfcRepresentation.RepresentationType, SELF\IfcRepresentation.Items);
END_ENTITY;

 EXPRESS-G diagram

	Form - Repräsentation
	Shape Representation
	Représentation de forme