IfcIntersectionCurve

BACnet MVD

#### IfcIntersectionCurve

Natural language names

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC4 Addendum 2
IfcIntersectionCurve |  |  | ADDED |

##### Semantic definitions at the entity

Entity definition

An IfcIntersectionCurve is a 3-dimensional curve that has two additional representations provided by two pcurves defined within two distinct and intersecting surfaces.

> NOTE Definition according to ISO/CD 10303-42:1992
> An intersection curve is a type of surface curve, which results from the intersection of two surfaces. It is represented as a special subtype of the surface curve entity having two distinct surface associations defined via the associated geometry list.

> NOTE Entity adapted from intersection_curve defined in ISO 10303-42.

> HISTORY New entity in IFC4 Add2.

Formal Propositions

Rule | Description
--- | ---
TwoPCurves | The intersection curve shall have precisely two associated geometry elements.
DistinctSurfaces | The two associated geometry elements shall be related to distinct surfaces. These are the surfaces which define the intersection curve.

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
IfcRepresentationItem

LayerAssignment

IfcPresentationLayerAssignment
@AssignedItems

S[0:1]

Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.

> IFC2x3 CHANGE The inverse attribute LayerAssignments has been added.

> IFC4 CHANGE The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.

X

StyledByItem

IfcStyledItem
@Item

S[0:1]

Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.

> IFC2x3 CHANGE The inverse attribute StyledByItem has been added.

X

X

IfcGeometricRepresentationItem
IfcCurve
| Dim :=IfcCurveDim(SELF) | IfcDimensionCount |  | The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve. | X | X
IfcSurfaceCurve
1 | Curve3D | IfcCurve |  | The curve which is the three-dimensional representation of the surface curve. |  | X
2 | AssociatedGeometry | IfcPcurve | L[1:2] | A list of one or two pcurves which define the surface or surfaces associated with the surface curve. Two elements in this list indicate that the curve has two surface associations which need not be two distinct surfaces. Being a pcurve, it also associates a basis curve in the parameter space of this surface as an alternative representation of the surface curve. |  | X

3

MasterRepresentation

IfcPreferredSurfaceCurveRepresentation

The defines the curve used to determine the unique parametrisation of the IfcSurfaceCurve.
The master_representation takes one of the values Curve3D, PCurve_S1 or PCurve_S2 to indicate a preference for the 3D curve, or the first or second pcurve, in the associated geometry list, respectively. Multiple representations provide the ability to communicate data in more than one form, even though the data is expected to be geometrically identical.
NOTE The master representation attribute acknowledges the impracticality of ensuring that multiple forms are indeed identical and allows the indication of a preferred form. This would probably be determined by the creator of the data. All characteristics, such as parametrisation, domain, and results of evaluation, for an entity having multiple representations, are derived from the master representation. Any use of the other representations is a compromise for practical considerations.

X

| BasisSurface :=IfcGetBasisSurface(SELF) | IfcSurface | S[1:2] | The surface, or surfaces on which the IfcSurfaceCurve lies. This is determined from the AssociatedGeometry list. |  | X
IfcIntersectionCurve

##### Formal representations

XML Specification
`<xs:element name="IfcIntersectionCurve" type="ifc:IfcIntersectionCurve" substitutionGroup="ifc:IfcSurfaceCurve" nillable="true"/>
<xs:complexType name="IfcIntersectionCurve">
<xs:complexContent>
<xs:extension base="ifc:IfcSurfaceCurve"/>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcIntersectionCurve
SUBTYPE OF (IfcSurfaceCurve);
WHERE
TwoPCurves : SIZEOF(SELF\IfcSurfaceCurve.AssociatedGeometry) = 2;
DistinctSurfaces : IfcAssociatedSurface(SELF\IfcSurfaceCurve.AssociatedGeometry[1]) <> IfcAssociatedSurface(SELF\IfcSurfaceCurve.AssociatedGeometry[2]);
END_ENTITY;

EXPRESS-G diagram

`

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