## 8.9.2.12 IfcTransitionCode

### 8.9.2.12.1 Semantic definitions at the entity

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 1 illustrates transition types

NOTE The figure is quoted from ISO 10303-42.

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

#### Items

##### DISCONTINUOUS

##### CONTINUOUS

The segments join but no condition on their tangents is implied.

##### CONTSAMEGRADIENT

The 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.

##### CONTSAMEGRADIENTSAMECURVATURE

For 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.

### 8.9.2.12.1 Formal representations

TYPE IfcTransitionCode = ENUMERATION OF
(DISCONTINUOUS
,CONTINUOUS
,CONTSAMEGRADIENT
,CONTSAMEGRADIENTSAMECURVATURE);
END_TYPE;