Zusammengesetzte Kurve | |

Composite Curve | |

Courbe composite |

Item | SPF | XML | Change | Description |
---|---|---|---|---|

IFC4 Addendum 1 |
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IfcCompositeCurve | ||||

SelfIntersect | MODIFIED | Type changed from LOGICAL to IfcLogical. | ||

IFC4x2 FINAL |
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IfcCompositeCurve | ||||

PositioningElement | ADDED |

An IfcCompositeCurve is a continuous curve composed of curve segments.

Figure 371 illustrates an example of a composite curve.

Figure 371 — 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 from0toland for_{1}i≤2, theisegment is parameterized from:^{th}where

lis the parametric length (i.e., difference between maximum and minimum parameter values) of the curve underlying the_{k}ksegment. Let^{th}Tdenote the parameter for the composite curve. Then, if theith segment is not a reparameterised composite curve segment,Tis related to the parametert;_{i}t_{i0}≤t_{i}≤t; for the_{i1}ith segment by the equation:ifSegments[i].SameSense= TRUE;or by the equation:

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

whereτis defined at reparameterized composite curve segment (seeIfcReparameterizedCompositeCurveSegment).

NOTE Entity adapted fromcomposite_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 | Cardinality | Description | G |
---|---|---|---|---|---|

1 | Segments | IfcCompositeCurveSegment | L[1:?] | 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. | X |

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

NSegments :=SIZEOF(Segments) | IfcInteger | The number of component curves. | X | ||

ClosedCurve :=Segments[NSegments].Transition <> Discontinuous | IfcLogical | Indication whether the curve is closed or not; this is derived from the transition code of the last segment. | X |

Rule | Description |
---|---|

CurveContinuous | No transition code should be Discontinuous, except for the last code of an open curve. |

SameDim | Ensures, that all segments used in the curve have the same dimensionality. |

# | Attribute | Type | Cardinality | Description | G |
---|---|---|---|---|---|

IfcRepresentationItem | |||||

LayerAssignment | IfcPresentationLayerAssignment @AssignedItems | S[0:1] | 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 IFC4 CHANGE The inverse attribute | X | |

StyledByItem | IfcStyledItem @Item | S[0:1] | 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 | X | |

IfcGeometricRepresentationItem | |||||

IfcCurve | |||||

Dim :=IfcCurveDim(SELF) | IfcDimensionCount | The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve. | X | ||

IfcBoundedCurve | |||||

PositioningElement | IfcLinearPositioningElement @Axis | ? | X | ||

IfcCompositeCurve | |||||

1 | Segments | IfcCompositeCurveSegment | L[1:?] | 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. | X |

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

NSegments :=SIZEOF(Segments) | IfcInteger | The number of component curves. | X | ||

ClosedCurve :=Segments[NSegments].Transition <> Discontinuous | IfcLogical | Indication whether the curve is closed or not; this is derived from the transition code of the last segment. | X |

` <xs:element name="IfcCompositeCurve" type="ifc:IfcCompositeCurve" substitutionGroup="ifc:IfcBoundedCurve" nillable="true"/>`

<xs:complexType name="IfcCompositeCurve">

<xs:complexContent>

<xs:extension base="ifc:IfcBoundedCurve">

<xs:sequence>

<xs:element name="Segments">

<xs:complexType>

<xs:sequence>

<xs:element ref="ifc:IfcCompositeCurveSegment" maxOccurs="unbounded"/>

</xs:sequence>

<xs:attribute ref="ifc:itemType" fixed="ifc:IfcCompositeCurveSegment"/>

<xs:attribute ref="ifc:cType" fixed="list"/>

<xs:attribute ref="ifc:arraySize" use="optional"/>

</xs:complexType>

</xs:element>

</xs:sequence>

<xs:attribute name="SelfIntersect" type="ifc:IfcLogical" use="optional"/>

</xs:extension>

</xs:complexContent>

</xs:complexType>

```
ENTITY IfcCompositeCurve
```

SUPERTYPE OF(IfcCompositeCurveOnSurface)

SUBTYPE OF (IfcBoundedCurve)**;**

Segments : LIST [1:?] OF IfcCompositeCurveSegment;

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;

References: IfcSectionedSpine IfcCompositeCurveSegment