8.9.3.59 IfcSeamCurve
8.9.3.59.1 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.
NOTE&bbsp; The `seam' on a cylinder has representations as the lines u = 0 or u = 360 degrees in parameter space.Figure 8.9.3.59.A shows an instance diagram explaining the use of IfcSeamCurve as a boundary curve of an IfcCylindricalSurface.
8.9.3.59.2 Entity inheritance
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- IfcCurve
- IfcAnnotationFillArea
- IfcBooleanResult
- IfcBoundingBox
- IfcCartesianPointList
- IfcCartesianTransformationOperator
- IfcCsgPrimitive3D
- IfcDirection
- IfcFaceBasedSurfaceModel
- IfcFillAreaStyleHatching
- IfcFillAreaStyleTiles
- IfcGeometricSet
- IfcHalfSpaceSolid
- IfcLightSource
- IfcPlacement
- IfcPlanarExtent
- IfcPoint
- IfcSectionedSpine
- IfcSegment
- IfcShellBasedSurfaceModel
- IfcSolidModel
- IfcSurface
- IfcTessellatedItem
- IfcTextLiteral
- IfcVector
8.9.3.59.3 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. The inverse attribute LayerAssignments has been added. The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed. |
|
| 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. The inverse attribute StyledByItem has been added. |
|
| 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. |
| 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. The master representation attribute acknowledges the impracticality of ensuring that multiple forms are indeed identical and allows the indication of a preferred form. This would probably be determined by the creator of the data. All characteristics, such as parametrisation, domain, and results of evaluation, for an entity having multiple representations, are derived from the master representation. Any use of the other representations is a compromise for practical considerations. |
| * | BasisSurface | SET [1:2] OF IfcSurface |
This attribute is formally derived. The surface, or surfaces on which the IfcSurfaceCurve lies. This is determined from the AssociatedGeometry list. |
8.9.3.59.4 Formal propositions
| Name | Description |
|---|---|
| SameSurface |
The two associated geometries shall be related to the same surface. |
|
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| TwoPCurves |
The intersection curve shall have precisely two associated geometry elements. |
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8.9.3.59.5 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;