IfcShapeRepresentation

BACnet MVD

#### IfcShapeRepresentation

Natural language names

| Form - Repräsentation
| Shape Representation
| Représentation de forme

##### 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 48 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 | 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)
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
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 48 — Representation identifiers

Several representation types for shape representation are included as predefined values for RepresentationType. Table 49 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 49 — 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 | B
--- | --- | --- | --- | --- | ---
IfcRepresentation
1 | ContextOfItems | IfcRepresentationContext |  | Definition of the representation context for which the different subtypes of representation are valid. | X | X
2 | RepresentationIdentifier | IfcLabel | ? | The optional identifier of the representation as used within a project. | X | 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

X

4 | Items | IfcRepresentationItem | S[1:?] | Set of geometric representation items that are defined for this representation. | X | 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

##### Examples

- CSG primitive
- Extruded solid
- Surface model
- Brep model
- Tessellated item
- Bath CSG Solid
- Cube advanced Brep
- Basin advanced brep
- Mapped shape without transformation
- Mapped shape with transformation
- Mapped shape with multiple items
- Air terminal element

##### 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

`

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