AreaBuilder

The input lines must be topologically correct and must neither self-intersect nor intersect each other. They must close at their endpoints. If these conditions are met, any area features implied by the input lines are created. (In addition to the Snapping Pre-Processing Parameters, you can also use the Snapper, Intersector, and MRF2DCleaner to clean data that does not meet these conditions before it enters this transformer.) This transformer can also create polygons and donuts (holes/islands). Any lines that cannot be formed into polygons are joined together to create maximum length linestrings.

Contains the output polygons.

Contains any lines that did not close. If Create Donuts is checked, it also contains degenerate polygons.

Contains any geometries that were rejected.

The default behavior is to use the entire set of input features as the group. This option allows you to select attributes that define which groups to form – each set of features that have the same value for all of these attributes will be processed as an independent group.

No attributes other than the Group By ones will be carried across from the Input features to the output features.

Note: How parallel processing works with FME: see About Parallel Processing for detailed information.

This parameter determines whether or not the transformer should perform the work across parallel processes. If it is enabled, a process will be launched for each group specified by the Group By parameter.

Parallel Processing Levels

For example, on a quad-core machine, minimal parallelism will result in two simultaneous FME processes. Extreme parallelism on an 8-core machine would result in 16 simultaneous processes.

You can experiment with this feature and view the information in the Windows Task Manager and the Workbench Log window.

No: This is the default behavior. Processing will only occur in this transformer once all input is present.

By Group: This transformer will process input groups in order. Changes of the value of the Group By parameter on the input stream will trigger batch processing on the currently accumulating group. This will improve overall speed if groups are large/complex, but could cause undesired behavior if input groups are not truly ordered.

Considerations for Using Input is Ordered By

Using Ordered input can provide performance gains in some scenarios, however, it is not always preferable, or even possible. Consider the following when using it, with both one- and two-input transformers.

Single Datasets/Feature Types: Are generally the optimal candidates for Ordered processing. If you know that the dataset is correctly ordered by the Group By attribute, using Input is Ordered By can improve performance, depending on the size and complexity of the data.

If the input is coming from a database, using ORDER BY in a SQL statement to have the database pre-order the data can be an extremely effective way to improve performance. Consider using a Database Readers with a SQL statement, or the SQLCreator transformer.

Multiple Datasets/Feature Types: Since all features matching a Group By value need to arrive before any features (of any feature type or dataset) belonging to the next group, using Ordering with multiple feature types is more complicated than processing a single feature type.

Multiple feature types and features from multiple datasets will not generally naturally occur in the correct order.

One approach is to send all features through a Sorter, sorting on the expected Group By attribute. The Sorter is a feature-holding transformer, collecting all input features, performing the sort, and then releasing them all. They can then be sent through an appropriate filter (TestFilter, AttributeFilter, GeometryFilter, or others), which are not feature-holding, and will release the features one at a time to the transformer using Input is Ordered By, now in the expected order.

The processing overhead of sorting and filtering may negate the performance gains you will get from using Input is Ordered By. In this case, using Group By without using Input is Ordered By may be the equivalent and simpler approach.

In all cases when using Input is Ordered By, if you are not sure that the incoming features are properly ordered, they should be sorted (if a single feature type), or sorted and then filtered (for more than one feature or geometry type).

As with many scenarios, testing different approaches in your workspace with your data is the only definitive way to identify performance gains.

Specifies whether curve endpoints must be connected in X,Y, and Z before being joined together (as opposed to just X, and Y). Note that if this is set to No, then the Connect in Z Mode parameter will specify how the Z values of segments that are not connected in 3D should be treated.

When viewed in 2D (ignoring Z), a path (which may define the border of a polygon) may appear to be closed as shown in the left figure below. This same path, when viewed in 3D, may appear to be open as shown in the right figure below.

To specify how (and if) paths should be closed in 3D, select one of the listed modes.

Mode	Description	Example
Extend	The Curve is extended so that all vertices are left at their original location.
Average	Subsequent vertices that are not connected, but share an x and a y value are combined into one vertex, whose Z value is the average of the original two.
First Wins	Subsequent vertices that are not connected, but share an x and a y value are combined into one vertex, whose Z value is taken from the first encountered vertex.
Last Wins	Subsequent vertices that are not connected, but share an x and a y value are combined into one vertex, whose Z value is taken from the last encountered vertex.
Ignore	Z values are ignored. No change is made to the way the nodes are connected.

If set to Yes, then when lines originating from different input curves are concatenated into a longer curve in the output, they will be left as separate segments in a path. The default is No, which means that such lines will be joined into longer lines in the output unless they have different properties (for example, traits, measures, geometry name).

Specifies that coordinate "cycles" within a polygon are allowable and will be constructed; such polygons might be considered invalid by other parts of FME or by output formats. A "cycle" is a line segment that occurs twice in the same polygon's boundary (once in each direction).

Specifies if the direction of the input curves needs to be considered while building polygons. If set to Yes, only curves that are tip-to-tail will result in polygons, all others will be output through the “Incomplete” port.

If checked, the resulting polygons will contain holes created by any other resulting polygons they completely contained. Following this, any holes that share a common edge will be dissolved together to make a larger hole.

If unchecked, the resulting polygons are output via the Area port. Note that if you want to create donut polygons, you will need to use the DonutBuilder.

Yes: Polygons that are holes of another polygon will not be output.

No: Polygons that are holes of another polygon will be output.

If Drop Incoming Attributes is chosen, the output feature will not preserve any input attributes. If Merge Incoming Attributes is chosen, the output feature will merge all input attributes. If Use Attributes From One Feature is chosen, the output feature will get attributes from only one input feature.

If you enter a List Name, a list will be created on each output feature, containing an element for each input feature which contributed to that geometry, in order of appearance.

This parameter can also be used to preserve attributes from input features.

Note: List attributes are not accessible from the output schema in Workbench unless they are first processed using a transformer that operates on them, such as ListExploder or ListConcatenator. All list attribute transformers are displayed in the Contents pane of the Transformer Help under Lists. Alternatively, AttributeExposer can be used.

All Attributes: Every attribute from all input features that created an output feature will be added to the list specified in List Name.

Selected Attributes: Only the attributes specified in the Selected Attributes parameter will be added to the list specified in List Name.

The attributes to be added to the list when Add To List is Selected Attributes.

An optional attribute to include in the generated list, which indicates whether the direction of that input feature has been preserved (using same) or reversed (using opposite) in the output feature.

When this parameter is set to None, no snapping takes place.

When this parameter is set to End Point Snapping, the transformer:

• Snaps end points of lines together if their distances are within the specified tolerance.

When this parameter is set to Vertex Snapping, the transformer does the following:

• Snaps vertices of lines together if their distances are within the specified tolerance.

When two features are snapped together, the feature that entered the factory most recently is the one that is modified.

Snapping Tolerance specifies the distance, in ground units, that the snapping occurs between features.