VoronoiCellGenerator

Outputs circular sectors of influence for point features that have directions defined by azimuths (degrees clockwise from North).

This transformer creates a number of sectors for each set of point features (collectively called a site), depending on each point’s direction of influence. Each sector fans out from the center point (site point) of the site it belongs to, and has a user-defined radius.

This transformer generates a Voronoi diagram that consists of polygons representing the closest areas around center points of sectors (site points). The final output will be the sectors truncated to the extents of their site’s corresponding Voronoi polygons.

This transformer has an additional output port that produces sectors truncated by Voronoi polygons, to eliminate possible overlaps between different sites.

Note To create sectors that may overlap with sectors of other sites, use the SectorGenerator transformer instead.

Example

In the telecommunications industry, directional antennas are used in conjunction with each other for better coverage and stronger signal reception. These antennas each cover a sector of a complete circle that an antenna tower covers, with some areas of overlap between each two sectors.

This transformer can be used to determine the “Nominal” (assuming a whole circle is covered and there are no overlaps between any two sectors) coverage field of directional antennas and receivers.

Input points and their azimuth values are received:

A center point is created for each site:

Note Please note that after this step, the locations of input points play no part in the generation of sectors, and the values that determine sectors are the input points’ azimuths and radii.

Polygon sectors are generated. The sector corresponding to each point will span an area determined by the radius set and:

(The point's azimuth + adjacent azimuth (in degrees))/2

Two sides of a sector are found by one time choosing the closest azimuth clockwise and the next time counter-clockwise. Resulting sectors will look like this:

Voronoi polygons are generated, based on site points:

If two sites have overlapping sectors, the sectors are clipped by the Voronoi polygons to generate Cells:

Configuration

Input Ports

Output Ports

Parameters

General

Site Name Attribute	This is the attribute that determines the site to which an input point belongs.
Azimuth Attribute	The direction each input point faces (or influences). The Azimuth Attribute is measured in degrees clockwise from North. Valid Azimuth Attribute values are positive and less than 360.
Sector Name Attribute	If a Sector Name Attribute is specified and there are points with the same sector name in a site, only one of the points is considered for creating sectors. Each feature entering the transformer is checked. If its sector name is already in use within its site, it will be output on the ExtraPoints port.
Radius	This parameter defines the radius of influence for each sector. This determines the radius of each sector in a site. Note Values of Radii larger than the extents of the area covered by the site points will produce invalid results. Differing values of radii for overlapping sectors will also result in incorrect output.
Maximum Distance Between Site Points	This parameter specifies the maximum distance a point can be from any other point in its site and still be considered in sector creation. Points are considered in the order they enter the transformer, with each new point tested against all other points already accepted as a part of its site. If a nonconstant value is specified for this parameter (for example, an attribute value, which may differ from feature to feature), then when comparing the distance between two features, the maximum distance will be calculated from the feature that entered the transformer earlier.
Ensure Topological Correctness	Yes: The output will form a well-noded coverage. Related transformers that expect this type of input include the TopologyBuilder, FeatureColorSetter, and similar transformers. No: There may be slight overlaps or gaps between sectors, making the output unsuitable for some geometric operations. Note that the input points should be in a way that the transformer is able to produce at least three different site points that are not collinear, since a Voronoi Diagram is generated for analysis.

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.

Text Editor

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.

Arithmetic Editor

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

String Functions	These functions manipulate and format strings.
Special Characters	A set of control characters is available in the Text Editor.
Math Functions	Math functions are available in both editors.
Date/Time Functions	Date and time functions are available in the Text Editor.
Math Operators	These operators are available in the Arithmetic Editor.
FME Feature Functions	These return primarily feature-specific values.
FME Parameters	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.

Row Reordering

Enabled once you have clicked on a row item. Choices include:

Add a row
Remove a row
Move current row up one
Move current row down one
Move current row to top
Move current row to bottom

Cut, Copy, and Paste

Enabled once you have clicked on a row item. Choices include:

Cut a row - delete and copy to clipboard
Copy a row to the clipboard
Paste a row from the clipboard

Cut, copy, and paste may be used within a transformer, or between transformers.

Filter

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.

Import

Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.

Reset/Refresh

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.

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