Defined in File Ifc4.h
IfcCompositeCurve: public Ifc4::IfcBoundedCurve¶
Definition from ISO/CD 10303-42:1992: 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 from 0 to l1 and for i ≤ 2, the ith segment is parameterized from:
where lk is the parametric length (i.e., difference between maximum and minimum parameter values) of the curve underlying the kth segment.
Let T denote the parameter for the composite curve. Then, if the ith segment is not a reparameterised composite curve segment, T is related to the parameter ti; ti0 ≤ ti ≤ ti1; for the ith 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 τ is defined at reparameterized composite curve segment (see IfcReparameterizedCompositeCurveSegment).
Figure 279 illustrates an example of a composite curve.
Figure 279 — 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 Corresponding ISO 10303 entity: composite_curve, please refer to ISO/IS 10303-42:1994, p. 56 for the final definition of the formal standard. The WR2 is added to ensure consistent Dim at all segments.
HISTORY New class in IFC Release 1.0
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.
Subclassed by Ifc4::IfcCompositeCurveOnSurface
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.
Indication of whether the curve intersects itself or not; this is for information only.