IFC 4.3.1.0 (IFC4X3_ADD1)

8.9.3.60 IfcSeamCurve

8.9.3.60.1 Semantic definition

An IfcSeamCurve is a 3-dimensional curve that has additional representations provided by exactly two distinct pcurves describing the same curve at the two extreme ends of a closed parametric surface.

Figure 8.9.3.60.A shows an instance diagram explaining the use of IfcSeamCurve as a boundary curve of an IfcCylindricalSurface.

seam curve usage
Figure 8.9.3.60.A — use of a seam curve bounding a cylindrical surface

8.9.3.60.2 Entity inheritance

8.9.3.60.3 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.

Click to show 3 hidden inherited attributes Click to hide 3 inherited attributes
IfcSurfaceCurve (4)
1 Curve3D IfcCurve

The curve which is the three-dimensional representation of the surface curve.

2 AssociatedGeometry LIST [1:2] OF IfcPcurve

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.

3 MasterRepresentation IfcPreferredSurfaceCurveRepresentation

The <em<MasterRepresentation 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.

* BasisSurface SET [1:2] OF IfcSurface

This attribute is formally derived.

IfcGetBasisSurface(SELF)

The surface, or surfaces on which the IfcSurfaceCurve lies. This is determined from the AssociatedGeometry list.

Table 8.9.3.60.B

8.9.3.60.4 Formal propositions

Name Description
SameSurface

The two associated geometries shall be related to the same surface.

IfcAssociatedSurface(SELF\IfcSurfaceCurve.AssociatedGeometry[1]) = IfcAssociatedSurface(SELF\IfcSurfaceCurve.AssociatedGeometry[2])
TwoPCurves

The intersection curve shall have precisely two associated geometry elements.

SIZEOF(SELF\IfcSurfaceCurve.AssociatedGeometry) = 2
Table 8.9.3.60.C

8.9.3.60.5 Formal representation

ENTITY IfcSeamCurve
 SUBTYPE OF (IfcSurfaceCurve);
 WHERE
	SameSurface : IfcAssociatedSurface(SELF\IfcSurfaceCurve.AssociatedGeometry[1]) = IfcAssociatedSurface(SELF\IfcSurfaceCurve.AssociatedGeometry[2]);
	TwoPCurves : SIZEOF(SELF\IfcSurfaceCurve.AssociatedGeometry) = 2;
END_ENTITY;

8.9.3.60.6 References

8.9.3.60.7 Changelog

8.9.3.60.7.1 IFC4

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