additions | where_rules | CurveContinuous |

additions | where_rules | SameDim |

deletions | where_rules | WR41 |

deletions | where_rules | WR42 |

modifications | attributes SelfIntersect definition | Changed from logical to IfcLogical |

modifications | attributes Segments definition | Changed from list[1:?] of IfcCompositeCurveSegment to list[1:?] of IfcSegment |

An *IfcCompositeCurve* is a continuous curve composed of curve segments.

Figure 1 illustrates an example of a composite curve.

Consider an *IfcCompositeCurve* having line segment and an arc segment. The line should be parameterized:

*IfcPolyline*with start= 0.,0. end= 0.,1.,*SameSense*= TRUE, parametric length = 1.

The arch should be parameterized:

*IfcTrimmedCurve*with start= 180', end= 90',*SameSense*= FALSE, parametric length = 90.

Then the parameterization of the composite curve is:

*IfcCompositeCurve*with 0. ≤ T ≤ 1. (line segment) and 1. ≤ T ≤ 91. (arc segment), parametric length = 91.

NOTE Definition according to ISO 10303-42:

A composite curve is a collection of curves joined end-to-end. The individual segments of the curve are themselves defined as composite curve segments. The parameterization of the composite curve is an accumulation of the parametric ranges of the referenced bounded curves. The first segment is parameterized from0tol~1~and fori__≤__2, thei^th^segment is parameterized from:where

l~k~is the parametric length (i.e., difference between maximum and minimum parameter values) of the curve underlying thek^th^segment. LetTdenote the parameter for the composite curve. Then, if thei_th segment is not a reparameterised composite curve segment, _Tis related to the parametert~i~;t~i0~__≤__t~i~__≤__t~i1~; for the _i_th segment by the equation:if

Segments[i].SameSense= TRUE; or by the equation:if

Segments[i].SameSense= FALSE; If the segments[i] is of type reparameterised composite curve segment,where

τis defined at reparameterized composite curve segment (seeIfcReparameterizedCompositeCurveSegment).NOTE Entity adapted from

composite_curvedefined in ISO 10303-42.HISTORY New entity in IFC1.0

Informal Propositions:

- The
*SameSense*attribute of each segment correctly specifies the senses of the component curves. When traversed in the direction indicated by*SameSense*, the segments shall join end-to-end.

# | Attribute | Type | Description |
---|---|---|---|

IfcRepresentationItem | |||

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. > 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. | |

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. > IFC2x3 CHANGE The inverse attribute StyledByItem has been added. | |

IfcGeometricRepresentationItem | |||

IfcCurve | |||

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

IfcBoundedCurve | |||

IfcCompositeCurve | |||

1 | Segments | LIST [1:?] OF IfcSegment | The component bounded curves, their transitions and senses. The transition attribute for the last segment defines the transition between the end of the last segment and the start of the first; this transition attribute may take the value discontinuous, which indicates an open curve. > NOTE : For IfcGradientCurve and IfcSegmentedReferenceCurve the segments define the interpolation between segment start and and segment end. |

2 | SelfIntersect | IfcLogical | Indication of whether the curve intersects itself or not; this is for information only. |

NSegments | INVALID | The number of component curves. | |

ClosedCurve | INVALID | Indication whether the curve is closed or not; this is derived from the transition code of the last segment. |

ENTITY IfcCompositeCurve SUPERTYPE OF (ONEOF (IfcCompositeCurveOnSurface ,IfcGradientCurve ,IfcSegmentedReferenceCurve)) SUBTYPE OF (IfcBoundedCurve); Segments : LIST [1:?] OF IfcSegment; SelfIntersect : IfcLogical; DERIVE NSegments : IfcInteger := SIZEOF(Segments); ClosedCurve : IfcLogical := Segments[NSegments].Transition <> Discontinuous; WHERE CurveContinuous : ((NOT ClosedCurve) AND (SIZEOF(QUERY(Temp <* Segments | Temp.Transition = Discontinuous)) = 1)) OR ((ClosedCurve) AND (SIZEOF(QUERY(Temp <* Segments | Temp.Transition = Discontinuous)) = 0)); SameDim : SIZEOF( QUERY( Temp <* Segments | Temp.Dim <> Segments[1].Dim)) = 0; END_ENTITY;