8.18.3.14 IfcShapeRepresentation

Représentation de forme
Form - Repräsentation

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 694 indicates the defined list of values for RepresentationIdentifier.

Identifier  
Box Bounding box as simplified 3D box geometry of an element
Annotation 2D 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)
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 694 — Representation identifiers

Several representation types for shape representation are included as predefined values for RepresentationType. Table 695 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
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)
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

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 695 — 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.

XSD 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
WR21 : 'IFCREPRESENTATIONRESOURCE.IFCGEOMETRICREPRESENTATIONCONTEXT' IN TYPEOF(SELF\IfcRepresentation.ContextOfItems);
WR22 : SIZEOF(QUERY(temp <* Items | ('IFCTOPOLOGYRESOURCE.IFCTOPOLOGICALREPRESENTATIONITEM' IN TYPEOF(temp)) AND (NOT(SIZEOF( ['IFCTOPOLOGYRESOURCE.IFCVERTEXPOINT', 'IFCTOPOLOGYRESOURCE.IFCEDGECURVE', 'IFCTOPOLOGYRESOURCE.IFCFACESURFACE'] * TYPEOF(temp)) = 1)) )) = 0;
WR23 : EXISTS(SELF\IfcRepresentation.RepresentationType);
WR24 : IfcShapeRepresentationTypes(SELF\IfcRepresentation.RepresentationType, SELF\IfcRepresentation.Items);
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

Formal Propositions:

WR21 : The context to which the IfcShapeRepresentation is assign, shall be of type IfcGeometricRepresentationContext.
WR22 : No topological representation item shall be directly used for shape representations, with the exception of IfcVertexPoint, IfcEdgeCurve, IfcFaceSurface.
WR23 : A representation type should be given to the shape representation.
WR24 : Checks the proper use of Items according to the RepresentationType.

Inheritance Graph:

ENTITY IfcShapeRepresentation
ENTITY IfcRepresentation
ContextOfItems : IfcRepresentationContext;
RepresentationIdentifier : OPTIONAL IfcLabel;
RepresentationType : OPTIONAL IfcLabel;
Items : SET [1:?] OF IfcRepresentationItem;
INVERSE
RepresentationMap : SET [0:1] OF IfcRepresentationMap FOR MappedRepresentation;
LayerAssignments : SET OF IfcPresentationLayerAssignment FOR AssignedItems;
OfProductRepresentation : SET OF IfcProductRepresentation FOR Representations;
ENTITY IfcShapeModel
INVERSE
OfShapeAspect : SET [0:1] OF IfcShapeAspect FOR ShapeRepresentations;
ENTITY IfcShapeRepresentation
END_ENTITY;

Examples:

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