Replaces area geometries with their approximate center lines, medial axes, or straight skeletons. This transformer works best with long, narrow areas.
Output Ports
Centerline
The center line of the input feature will be output via this port. If the input feature is an aggregate, at least one part was successfully processed, and the algorithm fails to generate a center line for another part, that part will be left unchanged.
<Rejected>
Features that cannot be replaced by their center line will be output via this port.
Rejected features will have an fme_rejection_code attribute with one of the following values:
INVALID_GEOMETRY
INVALID_GEOMETRY_TYPE
INVALID_POLYGON_NOT_SIMPLE
INVALID_ELLIPSE_NOT_SIMPLE
INVALID_DONUT_NOT_SIMPLE
Parameters
Mode
Approximate Center Line: The geometry of an area feature is replaced by an approximate center line. The approximate center line is calculated by performing a constrained Delaunay triangulation of the area feature, removing border triangles using a heuristic, creating new vertices at the midpoints of shared triangle edges and the midpoints of junction triangles, and combining all the new vertices into lines.
Medial Axis: The geometry of an area feature is replaced by its medial axis. The medial axis is the subset of the straight skeleton that does not include any edges that share a vertex with the original area.
Straight Skeleton: The geometry of an area feature is replaced by its straight skeleton (angular bisector network).
Note: In the medial axis or straight skeleton modes, the algorithm may take a long time to run on large or complex input features.
Usage Notes
- In the medial axis and straight skeleton modes, input areas must be non self-intersecting and simple (that is, the number of unique vertices must equal the number of edges)
- Because Z coordinates are not considered in any mode's algorithm, all features processed by this function are forced to 2D.
Example
Editing Transformer Parameters
Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click 
beside the applicable parameter. For more information, see Transformer Parameter Menu Options.
Transformer Categories
When combined with the Tester, this transformer enables FME to perform area generalization operations.
Technical History
Associated FME function or factory: @ConvertToLine
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Tags Keywords: abstraction simplification simplify centerline centreline CentreLineReplacer