FME Transformers: 2024.1
Categories and Related Transformers
Categories
Spatial Analysis
Related Transformers
2DBoxReplacer
2DGridAccumulator
2DGridCreator
BoundingBoxReplacer
BoundsExtractor
Creator
HullAccumulator
HullReplacer
MinimumSpanningCircleReplacer
RasterExtentsCoercer
Creates a rectangular polygon that spans the extents of all input features.
Typical Uses
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Determining the extents of an entire set of features
How does it work?
The BoundingBoxAccumulator receives features with any geometry type and creates the minimum enclosing rectangular polygon that contains all features. The rectangle is not rotated. Its sides are parallel to the x and y axes.
If features are 3D, including point clouds, the bounding box will contain their footprint - that is, their x and y extents.
If an output bounding box has zero area (the bounding box of a single point or vertical line, for example), it will become a point or line as appropriate.
The output bounding box can retain attributes from the input features, either as a single set of attribute values or a list of values from all input features.
Examples
Example: Generating a bounding box for a set of linear features
In this example, we have a set of rapid transit lines and want to generate the bounding box that contains all features.
Note that they have an attribute containing the name of the line.
The features are routed into a BoundingBoxAccumulator.
In the parameters dialog, we enable Generate List to add a list attribute to the output bounding box. It is named Lines and will contain the LINE value from all input features.
One bounding box is produced, spanning all input features. Note the list attribute containing the LINE values.
Usage Notes
Creating Boxes and Rectangles
Creating rectangular geometry is a common task. These transformers do so in a variety of ways.
Rectangle Transformers Comparison
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Transformer |
Function |
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Creates one or more new features with box geometry of a specific size and position (when Geometry Object is Box). |
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Replaces an existing feature’s geometry with a box of a specific size and position. |
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Creates one rectangle that encompasses all features received. |
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Individually replaces the geometry of each feature with a rectangle that covers its extents. |
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Individually replaces the geometry of each raster feature with a rectangle that covers its extents (with various Extents Type options). |
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Extracts the coordinate values that describe an individual feature’s bounding box (or cube) and stores them as attributes. |
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Creates a series of regularly-spaced rectangles that span the extent of all features received (when Type of Grid to Create is Polygons). |
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Creates a series of regularly-spaced rectangles of a specific size and position (when Type of Grid to Create is Polygons). |
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Tiler and RasterTiler |
Do not create actual rectangles, but chop features into a series of rectangular tiles, specified in a similar fashion to the 2DGridAccumulator. |
Configuration
Input Ports
Input
Features with geometry.
Output Ports
BoundingBox
A rectangle spanning the extent of all input features, optionally with attributes as specified in parameters.
<Rejected>
Features without valid geometry are output via this port.
Rejected features will have an fme_rejection_code attribute with one of the following values:
INVALID_GEOMETRY_VERTICES
Rejected Feature Handling: can be set to either terminate the translation or continue running when it encounters a rejected feature. This setting is available both as a default FME option and as a workspace parameter.
Parameters
Group Processing
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Group By |
The input features may be partitioned into groups based on attribute values. One bounding box is output for each group. If Group By is not specified, all input features will be processed together and a single bounding box will be output. |
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Complete Groups
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Select the point in processing at which groups are processed:
Considerations for Using Group By
There are two typical reasons for using When Group Changes (Advanced) . The first is incoming data that is intended to be processed in groups (and is already so ordered). In this case, the structure dictates Group By usage - not performance considerations. The second possible reason is potential performance gains. Performance gains are most likely when the data is already sorted (or read using a SQL ORDER BY statement) since less work is required of FME. If the data needs ordering, it can be sorted in the workspace (though the added processing overhead may negate any gains). Sorting becomes more difficult according to the number of data streams. Multiple streams of data could be almost impossible to sort into the correct order, 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. In this case, using Group By with When All Features Received may be the equivalent and simpler approach. Note Multiple feature types and features from multiple datasets will not generally naturally occur in the correct order.
As with many scenarios, testing different approaches in your workspace with your data is the only definitive way to identify performance gains. |
Attribute Accumulation
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Accumulation Mode |
Drop Incoming Attributes: The bounding box receives no attributes. Merge Incoming Attributes: The bounding box receives all attributes from input features. Use Attributes From One Feature: The bounding box receives all attributes from one representative feature. |
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Generate List |
When enabled, adds a list attribute to the output bounding box with values from multiple input features.
Note List attributes are not accessible from the output schema in FME Workbench unless they are first processed using a transformer that operates on them, such as ListExploder or ListConcatenator. Alternatively, AttributeExposer can be used.
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Editing Transformer Parameters
Transformer parameters can be set by directly entering values, using expressions, or referencing other elements in the workspace such as attribute values or user parameters. Various editors and context menus are available to assist. To see what is available, click 
beside the applicable parameter.
How to Set Parameter Values
Defining Values
There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters.
Using the Text Editor
The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.
Using the Arithmetic Editor
The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.
Conditional Values
Set values depending on one or more test conditions that either pass or fail.
Parameter Condition Definition Dialog
Content
Expressions and strings can include a number of functions, characters, parameters, and more.
When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.
Content Types
| These functions manipulate and format strings. | |
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Special Characters |
A set of control characters is available in the Text Editor. |
| Math functions are available in both editors. | |
| Date/Time Functions | Date and time functions are available in the Text Editor. |
| These operators are available in the Arithmetic Editor. | |
| These return primarily feature-specific values. | |
| FME and workspace-specific parameters may be used. | |
| Creating and Modifying User Parameters | Create your own editable parameters. |
Dialog Options - Tables
Table Tools
Transformers with table-style parameters have additional tools for populating and manipulating values.
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Row Reordering
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Enabled once you have clicked on a row item. Choices include:
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Cut, Copy, and Paste
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Enabled once you have clicked on a row item. Choices include:
Cut, copy, and paste may be used within a transformer, or between transformers. |
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Filter
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Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output. |
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Import
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Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers. |
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Reset/Refresh
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Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers. |
Note: Not all tools are available in all transformers.
For more information, see Transformer Parameter Menu Options.
Reference
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Processing Behavior |
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Feature Holding |
Yes |
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Dependencies |
None |
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Aliases |
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History |
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FME Community
The FME Community is the place for demos, how-tos, articles, FAQs, and more. Get answers to your questions, learn from other users, and suggest, vote, and comment on new features.
Search for all results about the BoundingBoxAccumulator on the FME Community.
Examples may contain information licensed under the Open Government Licence – Vancouver, Open Government Licence - British Columbia, and/or Open Government Licence – Canada.