IFC (IFC4X3) development IfcOffsetCurve2D Semantic definition

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

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: Math 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.
Figure Entity inheritance Attributes

# Attribute Type Description
IfcRepresentationItem (2)
LayerAssignment SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems

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.

StyledByItem SET [0:1] OF IfcStyledItem FOR Item

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

IfcCurve (1)
* Dim IfcDimensionCount

This attribute is formally derived.


The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.

IfcOffsetCurve (1)
1 BasisCurve IfcCurve

The curve that is being offset.

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IfcOffsetCurve2D (2)
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).)

3 SelfIntersect IfcLogical

An indication of whether the offset curve self-intersects; this is for information only.

Table Formal propositions

Name Description

The underlying curve shall be defined in two-dimensional space.

BasisCurve.Dim = 2
Table Formal representation

ENTITY IfcOffsetCurve2D
 SUBTYPE OF (IfcOffsetCurve);
	Distance : IfcLengthMeasure;
	SelfIntersect : IfcLogical;
	DimIs2D : BasisCurve.Dim = 2;

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Is this page difficult to understand? Let us know! Changelog

  • where rule, DimIs2D
  • where rule, WR1
  • attribute SelfIntersect type, Changed from "logical" to "IfcLogical"