IfcTransitionCode

Natural language names
Transition Code
Enumération des types de transition
Semantic definitions at the type
Type definition

The IfcTransitionCode indicated the continuity between consecutive segments of a curve or surface.

EXAMPLE  In ContSameGradient the tangent vectors of successive segments will have the same direction, but may have different magnitude.

Figure 356 illustrates transition types

NOTE  The figure is quoted from ISO 10303-42.

"transition code"

Figure 356 — Transition code

NOTE  Definition according to ISO/CD 10303-42:1992
This type conveys the continuity properties of a composite curve or surface. The continuity referred to is geometric, not parametric continuity.

NOTE  Type adapted from transition_code defined in ISO 10303-42.

HISTORY  New Type in IFC1.0

Enumeration definition
ConstantDescription
DISCONTINUOUSThe segments do not join. This is permitted only at the boundary of the curve or surface to indicate that it is not closed.
CONTINUOUSThe segments join but no condition on their tangents is implied.
CONTSAMEGRADIENTThe segments join and their tangent vectors or tangent planes are parallel and have the same direction at the joint: equality of derivatives is not required.
CONTSAMEGRADIENTSAMECURVATUREFor a curve, the segments join, their tangent vectors are parallel and in the same direction and their curvatures are equal at the joint: equality of derivatives is not required. For a surface this implies that the principle curvatures are the same and the principle directions are coincident along the common boundary.
Formal representations
XML Specification
 <xs:simpleType name="IfcTransitionCode">
  <xs:restriction base="xs:string">
   <xs:enumeration value="discontinuous"/>
   <xs:enumeration value="continuous"/>
   <xs:enumeration value="contsamegradient"/>
   <xs:enumeration value="contsamegradientsamecurvature"/>
  </xs:restriction>
 </xs:simpleType>
EXPRESS Specification
TYPE IfcTransitionCode = ENUMERATION OF (
 DISCONTINUOUS,
 CONTINUOUS,
 CONTSAMEGRADIENT,
 CONTSAMEGRADIENTSAMECURVATURE);
END_TYPE;

Link to EXPRESS-G diagram EXPRESS-G diagram

References  References: IfcCompositeCurveSegment

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