IfcPcurve

BACnet MVD

#### IfcPcurve

Natural language names

| Kurve im Parameterraum einer Fläche
| Pcurve
| Courbe basée sur une surface

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC2x3 to IFC4
IfcPcurve |  |  | ADDED |

##### Semantic definitions at the entity

Entity definition

The IfcPcurve is a curve defined within the parameter space of its reference surface.

> NOTE Definition according to ISO/CD 10303-42:1992
> A pcurve is a curve which lies on the basis of a surface and is defined in the parameter space of that surface. The basis curve is a curve defined in the two-dimensional parametric space of a reference basis surface. Although it is defined by a curve in two dimensional space, the variables involved are u and v, which occur in the parametric representation of the referenced surface, rather than the x, y, Cartesian coordinates. The basis curve is only defined within the parametric range of the surface.

> NOTE Entity adapted from pcurve in ISO 10303-42.

> HISTORY New entity in IFC4.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
1 | BasisSurface | IfcSurface |  |  | X | X
2 | ReferenceCurve | IfcCurve |  |  | X | X

Formal Propositions

Rule | Description
--- | ---
DimIs2D | The dimensionality of the parameter space curve shall be 2.

##### 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
IfcPcurve
1 | BasisSurface | IfcSurface |  |  | X | X
2 | ReferenceCurve | IfcCurve |  |  | X | X

##### Formal representations

XML Specification
`<xs:element name="IfcPcurve" type="ifc:IfcPcurve" substitutionGroup="ifc:IfcCurve" nillable="true"/>
<xs:complexType name="IfcPcurve">
<xs:complexContent>
<xs:extension base="ifc:IfcCurve">
<xs:sequence>
<xs:element name="BasisSurface" type="ifc:IfcSurface" nillable="true"/>
<xs:element name="ReferenceCurve" type="ifc:IfcCurve" nillable="true"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcPcurve
SUBTYPE OF (IfcCurve);
BasisSurface : IfcSurface;
ReferenceCurve : IfcCurve;
WHERE
DimIs2D : ReferenceCurve.Dim = 2;
END_ENTITY;

EXPRESS-G diagram

`

References: IfcSurfaceCurve IfcCurveOnSurface

Link to this page