IfcOffsetCurve2D

BACnet MVD

#### IfcOffsetCurve2D

Natural language names

| Versetzte Kurve im zweidimensionalen Raum (2D)
| Offset Curve2 D
| Décalage de courbe 2D

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC4 Addendum 1
IfcOffsetCurve2D |  |  |  |
SelfIntersect |  |  | MODIFIED | Type changed from LOGICAL to IfcLogical.

##### Semantic definitions at the entity

Entity definition

An IfcOffsetCurve2D is a curve defined by an offset in 2D space from its BasisCurve.

> NOTE Definition according to ISO/CD 10303-42:1992
> An offset curve 2d is a curve at a constant distance from a basis curve in two-dimensional space. This entity defines a simple plane-offset curve by offsetting by distance along the normal to basis curve in the plane of basis curve. The underlying curve shall have a well-defined tangent direction at every point. In the case of a composite curve, the transition code between each segment shall be cont same gradient or cont same gradient same curvature.

> > NOTE The offset curve 2d may differ in nature from the basis curve; the offset of a non self- intersecting curve can be self-intersecting. Care should be taken to ensure that the offset to a continuous curve does not become discontinuous.

> The offset curve 2d takes its parameterization from the basis curve. The offset curve 2d is parameterized as:

> where T is the unit tangent vector to the basis curve C(u) at parameter value u, and d is distance. The underlying curve shall be two-dimensional.

> NOTE Entity adapted from offset_curve_2d defined in ISO 10303-42.

> HISTORY New entity in IFC2x

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
1 | BasisCurve | IfcCurve |  | The curve that is being offset. |  | X
2 | Distance | IfcLengthMeasure |  | The distance of the offset curve from the basis curve. distance may be positive, negative or zero. A positive value of distance defines an offset in the direction which is normal to the curve in the sense of an anti-clockwise rotation through 90 degrees from the tangent vector T at the given point. (This is in the direction of orthogonal complement(T).) |  | X
3 | SelfIntersect | IfcLogical |  | An indication of whether the offset curve self-intersects; this is for information only. |  | X

Formal Propositions

Rule | Description
--- | ---
DimIs2D | The underlying curve shall be defined in two-dimensional space.

##### 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
IfcOffsetCurve2D
1 | BasisCurve | IfcCurve |  | The curve that is being offset. |  | X
2 | Distance | IfcLengthMeasure |  | The distance of the offset curve from the basis curve. distance may be positive, negative or zero. A positive value of distance defines an offset in the direction which is normal to the curve in the sense of an anti-clockwise rotation through 90 degrees from the tangent vector T at the given point. (This is in the direction of orthogonal complement(T).) |  | X
3 | SelfIntersect | IfcLogical |  | An indication of whether the offset curve self-intersects; this is for information only. |  | X

##### Formal representations

XML Specification
`<xs:element name="IfcOffsetCurve2D" type="ifc:IfcOffsetCurve2D" substitutionGroup="ifc:IfcCurve" nillable="true"/>
<xs:complexType name="IfcOffsetCurve2D">
<xs:complexContent>
<xs:extension base="ifc:IfcCurve">
<xs:sequence>
<xs:element name="BasisCurve" type="ifc:IfcCurve" nillable="true"/>
</xs:sequence>
<xs:attribute name="Distance" type="ifc:IfcLengthMeasure" use="optional"/>
<xs:attribute name="SelfIntersect" type="ifc:IfcLogical" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcOffsetCurve2D
SUBTYPE OF (IfcCurve);
BasisCurve : IfcCurve;
Distance : IfcLengthMeasure;
SelfIntersect : IfcLogical;
WHERE
DimIs2D : BasisCurve.Dim = 2;
END_ENTITY;

EXPRESS-G diagram

`

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