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8.9.3.41 IfcOffsetCurve3D

8.9.3.41.1 Semantic definition

An IfcOffsetCurve3D is a curve defined by an offset in 3D space from its BasisCurve.

{ .extDef}

NOTE The offset curve 3d 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 3d takes its parameterization from the basis curve. The offset curve 3d is parameterized as: Math 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 three-dimensional.
Figure A

Informal Propositions

  1. At no point on the curve shall ref direction be parallel, or opposite to, the direction of the tangent vector.

8.9.3.41.2 Entity inheritance

8.9.3.41.3 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. 

 IfcCurveDim(SELF)

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.
Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes
IfcOffsetCurve3D (3)
2 Distance IfcLengthMeasure

The distance of the offset curve from the basis curve. The distance may be positive, negative or zero.
3 SelfIntersect IfcLogical

An indication of whether the offset curve self-intersects, this is for information only.
4 RefDirection IfcDirection

The direction used to define the direction of the offset curve 3d from the basis curve.
Table B

8.9.3.41.4 Formal propositions

Name Description
DimIs2D

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

 
BasisCurve.Dim = 3
Table C

8.9.3.41.5 Formal representation 

ENTITY IfcOffsetCurve3D
SUBTYPE OF (IfcOffsetCurve);
Distance : IfcLengthMeasure;
SelfIntersect : IfcLogical;
RefDirection : IfcDirection;
WHERE
DimIs2D : BasisCurve.Dim = 3;
END_ENTITY;

Edit on Github

4 contributor(s): ArturTomczakbSI-BotThomas KrijnenDion Moult
Last change: Improve definition split (#876) * bring back headers headers were previously removed by mistake, now bringing them back * add new lines and rename the tag add the word 'short' in it * unify newlines make exactly one newline before and two after the tag * resolving typos Because bringing back headers required to go back in time to previous version, I'm now re-resolving the issues: #861, #860, #856 by ArturTomczak on 2024-07-16T16:07:28+02:00

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8.9.3.41.6 Changelog

8.9.3.41.6.1 IFC4

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

8.9.3.41.6.2 IFC4.1