Clipper

Example: Vector clipping - areas on lines

In this example, we start with two datasets - one with multiple park polygons, and the second with bike path lines. The bike paths run in and out of multiple parks, as can be seen here with the path selected and highlighted in yellow.

In the workspace, the parks are routed into the Clipper input port, and the bike paths are the Clippees - the features that will be altered according to the Clippers.

In the Clipper parameters dialog, Clipper Type is set to Multiple Clippers, as we have multiple park polygons and want to clip the paths with all of them.

This is a vector clip, and so we make the appropriate selections under Vector Parameters, including setting Create Aggregates to No - which determines how the output lines are handled.

Lastly, we enable Merge Attributes, which will transfer attributes from the parks (Clippers) to the lines (Clippees). By choosing Prefix Clipper, these new attributes will be prefixed with our string “Park_” and clearly indicate the source of the attribute.

The bike paths are split where they encounter a park boundary, receive attributes prefixed with Park_, and are output as either Inside or Outside feature types (shown here in blue and magenta).

Example: Raster clipping - area on rasters

In this example, we have a series of 40 orthophoto tiles, which we would like to clip to the city’s land boundary. The boundaries (extents) of each raster are overlaid in orange.

The boundary - a single polygon - is connected to the Clipper input port, and the series of TIFF images are connected to the Clippee port. Note that 40 individual TIFF files are read in, but only 32 will be sent out the Inside output port.

In the Clipper parameters dialog, we set Clipper Type to Single Clipper, which will improve performance in this case, where we do have only one Clipper area.

For a raster clipping operation, the only other parameters we need to look at are Raster Parameters, where we choose whether or not we want areas outside the clip boundary to be padded with nodata pixels to their original extents. No is the default, and fine for this case. (If you want the output rasters to retain their original dimensions, you would choose Yes.)

Of the 40 rasters that went in, 32 of them fell partially or entirely Inside the clip boundary. In the rasters that intersected the boundary, pixels that fall inside are untouched, but pixels that fall outside are set to nodata - indicated here by black.

This close-up shows the clipping of pixels (nodata - black) along the water boundary.

The extents of new rasters are shown here in orange. They are of varying size now, clipped tightly to the Clipper boundary (as we chose not to Preserve Clippee Extents).

Clipper Geometry Support Reference

This:	Can be clipped by:	Can clip:
Point/text	Area* Solid**	Nothing
Curve/line	Area*	Nothing
Area	Area*	Point/text Curve/line Area Solid Point Cloud Raster Multi/aggregates of the above
Surface	Nothing	Nothing
Solid	Area* Solid**	Point/text Solid Point Cloud Multi/aggregates of the above
Point cloud	Area* Solid**	Nothing
Raster	Area*	Nothing
Multi-point/aggregate	Area* Solid**	Nothing
Multi-curve/aggregate	Area*	Nothing
Multi-area/aggregate	Area*	Point/text Curve/line Area Solid Point Cloud Raster Multi/aggregates of the above
Multi-solid/aggregate	Area* Solid**	Point/text Solid Point Cloud Multi/aggregates of the above
No geometry	Nothing	Nothing

* Area as Clipper: includes polygons, ellipses, donuts, and aggregates (multi-) of them.

** Solid as Clipper: includes solids and aggregate (multi-) solids.

Spatial Transformers Comparison Matrix

Transformer	Can Merge Attributes	Alters Geometry	Counts Related Features	Creates List	Supported Types*	Recommended For
SpatialFilter	Yes	No	No	No	Point Text Curve Area	Testing for the existence of spatial relationships between two sets of features, and routing them according to whether they pass or fail the test(s).
SpatialRelator	Yes	No	Yes	Yes	Point Text Curve Area	Identifying the nature of spatial relationships between two sets of features.
AreaOnAreaOverlayer	Yes	Yes	Yes	Yes	Area	Finding polygon overlaps and extracting them into new geometry.
LineOnAreaOverlayer	Yes	Yes	Yes	Yes	Curve and Area	Finding intersections between lines and polygons, and splitting the lines where they intersect with the polygons.
LineOnLineOverlayer	Yes	Yes	Yes	Yes	Curve	Finding intersections between line features, splitting them, and generating new line geometry as well as points representing the intersections.
PointOnAreaOverlayer	Yes	No	Yes	Yes	Point and Area Text and Area	Identifying points that fall within polygons, and merging attributes between them
PointOnLineOverlayer	Yes	Yes	Yes	Yes	Point and Curve Text and Curve	Identifying where points fall on lines, and splitting the lines into new geometry.
PointOnPointOverlayer	Yes	No	Yes	Yes	Point Text	Identifying points in the same location (within a tolerance), and merging attributes between them.
Intersector	Yes	Yes	Yes	Yes	Point Text Curve Area	Finding intersections between all input features, regardless of geometry (optionally including self-intersections), splitting features, and creating new geometry.
Clipper	Yes	Yes	No	No	Point Text Curve Area Solids Raster Point Cloud	Comparing features against a set of Clipper features, and splitting the features at or along the Clipper boundaries. Outputs both new and untouched geometry, identified as either Inside or Outside the Clipper.
NeighborFinder	Yes	In some cases	No	Yes	Point Text Curve Area	Identifying the nearest other feature(s) to each feature being considered, either in another set of features or within the same feature set.
TopologyBuilder	Yes	Yes	No	Yes	Point Text Curve Area	Analyzing spatial relationships between features to compute topology, splitting features and creating new geometry representing topologically significant nodes, edges, and faces, with associated attributes.

* NOTE: Curve includes Lines, Arcs, and Paths. Area includes Polygons, Donuts, and Ellipses.

The Effect of Spatial Transformer Choice on Performance

Spatial analysis can be processing-intensive, particularly when a large number of features are involved. If you would like to tune the performance of your workspace, this is a good place to start.

When there are multiple ways to configure a workspace to reach the same goal, it is often best to choose the transformer most specifically suited to your task. As an example, when comparing address points to building polygons, there are a few ways to approach it.

The first example, using a SpatialFilter to test whether or not points fall inside polygons, produces the correct result. But the SpatialFilter is a fairly complex transformer, able to test for multiple conditions and accept a wide range of geometry types. It isn’t optimized for the specific spatial relationship we are analyzing here.

With a SpatialFilter:

The second example uses a PointOnAreaOverlayer, followed by a Tester. The features output are the same as in the first method, but the transformer is optimized for this specific task. The difference in processing time is substantial - from 54.3 seconds in the first configuration, down to 13.7 seconds in the second one.

With a PointOnAreaOverlayer and a Tester:

If performance is an issue in your workspace, look for alternative methods, guided by geometry.

Clipper

The features routed into the transformer via the Clipper port identify the area against which all Clippee features are processed. The Clipper can consist of any area features (polygons, donuts, or aggregate polygons/donuts). The Clipper can also be a solid or multi-solid if the Clippee input consists of solids, points, point clouds, or aggregates of these geometries. Any invalid clipping features that are encountered will be logged with a warning and discarded.

Clippee

Features to be clipped enter via the Clippee port.

Inside

Clippee features that are completely within the Clipper, and Clippee features that intersect the Clipper which were broken up into pieces. Those pieces that are on the inside of the Clipper are output via this port.

Outside

Clippee features completely outside of the Clipper are output via the Outside port, and Clippee features that intersect the Clipper which were broken up into pieces. Those pieces that are outside the clipping area are output via this port.

Invalid Clipper features (that is, non-polygon features) as well as invalid Clippee features (that is, features with no geometry) are output via the <Rejected> port.

Rejected features will have an fme_rejection_code attribute with one of the following values:

EXTRA_CLIPPER_FEATURE
INVALID_CLIPPER_GEOMETRY_TYPE.

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.

Transformer

Group By

The default behavior is to use the entire set of features as the group. This option allows you to select attributes that define which groups to form.

Clipper

Clipper Type

Single Clipper: Only a single Clipper feature will be used.

Multiple Clippers: All Clipper features will be used.

Clippers First: The Clipper assumes that all Clipper features will enter the transformer before any Clippee features. Any further Clipper features that arrive after the first Clippee will be logged with a warning and discarded.

Clipped Indicator Attribute

This attribute (if specified) will be added with a value of yes to any features output via either the Inside or Outside port which were cut by the transformer, and a value of no to any output features which were not changed by the transformer.

Z and Measures Parameters

Preserve Measures/Z From

Specifies where to take the measures and Z values from.

Clippee Only: All measures and Z values of the Clipper will be dropped.

Clipper Only: All measures and Z values from the Clippee will be dropped.

Clipper and Clippee: Measures and Z values from the Clippee and Clipper are used. The Connect Z Mode parameter will determine how z values are handled.

Connect Z Mode

If applicable, select a method for handling z values.

Connect Z Mode

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.

Measures/Z Conflict Value

This parameter specifies how to deal with geometries that have a measure, but are missing at least one value, or that have z values, but are missing at least one value.

None (Drop Values): Remove incomplete measures or z values.

Compute: Look at the values on either side of the missing value, and compute an estimate.

Custom Value: The missing values are filled in with the specified custom default value.

Treat Measures as

When using the Compute mode to compute missing measure values, measures can be considered Continuous, and linearly interpolated from their neighbors, or they can be Discrete, and taken exactly from the nearest neighbor.

Vector Parameters

Tolerance	The minimum distance between geometries in 2D before they are considered equal, in ground units. If the tolerance is None, the geometries must be exactly identical to be considered equal. If the tolerance is Automatic, a tolerance will be automatically computed based on the location of the input geometries. Additionally, a custom tolerance may be used.
Clippees on Clipper Boundary	This parameter directs what action should be taken with Clippee features that lie entirely on the boundary of the clipper. Treat as Inside: These features that lie on the boundary are output via the Inside port. Treat as Outside: These features that lie on the boundary are output via the Outside port. Treat as Inside and Outside: Points and line segments on the boundary are duplicated and output as both Inside and Outside.
Create Aggregates	If the Create Aggregates parameter is No, then features that are clipped into multiple parts will not be aggregated, but rather each part will be output as a separate feature.
Preserve Lines as Path Segments	Yes: Contiguous lines that constitute the boundary of the output features will be left as separate segments in a path. No: Such lines will be joined into longer lines in the output unless they have different properties (for example, traits, measures, and geometry name).

Raster Parameters

Preserve Clippee Extents

If this parameter is set to No, the Inside rasters which were clipped will be equal to the intersections of the clippers and clippees. Otherwise, the intersections will be padded by nodata so that the extents are identical to those of the input rasters.

Merge Attributes

When enabled, attributes on the Clipper will be merged onto the Clippee as defined by the parameters here. Otherwise, no attribute merging will take place.

If attributes on the Clipper and Clippee features share the same name, but are not geometry attributes that start with fme_, then they are deemed conflicted.

Accumulation Mode

Merge Clipper: The Clippee feature will retain all of its own un-conflicted attributes, and will additionally acquire any un-conflicted attributes that the Clipper feature has. This mode will handle conflicted attributes based on the Conflict Resolution parameter.

Prefix Clipper: The Clippee feature will retain all of its own attributes. In addition, the Clippee will acquire attributes reflecting the Clipper feature’s attributes, with the name prefixed with the Prefix parameter.

Only Use Clipper: The Clippee feature will have all of its attributes removed, except geometry attributes that start with fme_. Then, all of the attributes from one (arbitrary) Clipper feature will be placed onto the Clippee.

Conflict Resolution

Use Clippee: If a conflict occurs, the Clippee values will be maintained.

Use Clipper: If a conflict occurs, the values of the Clipper will be transferred onto the Clippee.

Prefix

If the Accumulation Mode parameter is set to Prefix Clipper, this value will prefix attributes that are being added to the Clippee feature from the Clipper feature.

How to Set Parameter Values

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 - whether entered directly in a parameter or constructed using one of the editors.

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.
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.
Working with User Parameters	Create your own editable parameters.

Related Transformers

PointOnPointOverlayer

SpatialFilter

SpatialRelator

TopologyBuilder

Processing Behavior	Group-Based
Feature Holding	Yes
Dependencies
FME Licensing Level	FME Professional Edition and above
Aliases
History
Categories	Spatial Analysis

Clipper

Typical Uses

How does it work?

What can I clip?

Usage Notes

Choosing a Spatial Transformer

Configuration

Input Ports

Output Ports

Parameters

Editing Transformer Parameters

Defining Values

Reference

FME Knowledge Center