PointCloudSorter

Sorts the points within a point cloud by one or more component values.

Typical Uses

Sorting point cloud points in preparation for further manipulation or analysis

How does it work?

The PointCloudSorter receives point cloud features, and re-orders the points within them according to selected component values. The sort order may be either ascending or descending.

Sorting may be done on more than one component, in which case the points are sorted primarily by the first selected component and order, secondarily by the second, and so on.

Multiple point clouds may be sorted, and each one will be sorted individually (not merged).

Examples

Example: Sorting a point cloud to find lowest points

In this example, we will use point cloud sorting to identify the lowest points in a point cloud, removing vegetation to produce a bare earth representation of the area.

Note that the source point cloud is a heavily forested area, shown here from an oblique angle in the FME Data Inspector, and the highest point is 145.92 meters.

We will use three steps to find the lowest points:

Round the x and y coordinates to a chosen grid size with a PointCloudExpressionEvaluator,
Sort the points by elevation with a PointCloudSorter, in ascending order, so the lowest points occur first, and
Merge the point cloud with itself to isolate the lowest point at each location, using a PointCloudMerger.

Step 1 - Round the coordinates

The point cloud is first routed into a PointCloudExpressionEvaluator. In the parameters dialog, the x and y components are recalculated, using an expression that rounds them to a specific interval - in this case, 10 meters.

Step 2 - Sort the points by elevation

Next, the point cloud is sent to a PointCloudSorter. In the parameters dialog, we sort based on the z component, in Ascending order.

The result of these first two transformers is a point cloud that still contains all original points, but they have been shifted onto a regular xy grid with 10 meter spacing, and internally, the points occur in ascending order of elevation and so will subsequently be processed in that order.

Step 3 - Isolate the lowest points

Next, the sorted point cloud is merged onto itself in a PointCloudMerger, routing a copy into both the Requestor and Supplier input ports.

The Referenced output port produces a point cloud containing the first occurrence of any given x,y pair. Since the lowest ones will be processed first due to the sorting, those are the points that will be kept.

(See the PointCloudMerger for a complete example of removing duplicates in a point cloud.)

In the parameters dialog, we join on the x and y components only - not z.

After sending the Referenced point cloud through a PointCloudPropertyExtractor (not shown in the workspace above) to calculate its new x, y, and z extents, we can see the bare earth representation as points spaced 10 meters apart, and with a new maximum elevation of 98.28 meters.

Usage Notes

Choosing a Point Cloud Transformer

FME has a selection of transformers for working specifically with point cloud data.

For information on point cloud geometry and properties, see Point Clouds (IFMEPointCloud).

Point Cloud Transformers

PointCloudCoercer	Converts point clouds to point or multipoint geometries, optionally retaining attribute and component values.
PointCloudCombiner	Combines features into a single point cloud. Point cloud and non-point cloud geometries are supported.
PointCloudComponentAdder	Adds new components with constant values to a point cloud.
PointCloudComponentCopier	Copies selected component values onto either a new or existing component
PointCloudComponentKeeper	Keeps only specified point cloud components, discarding all others.
PointCloudComponentRemover	Removes specified components from a point cloud.
PointCloudComponentRenamer	Renames an existing component.
PointCloudComponentTypeCoercer	Alters the data type of point cloud components, and converts component values if required.
PointCloudConsumer	Reads point cloud features for testing purposes, including any accumulated point cloud operations. No additional operations are performed, and nothing is done with the features.
PointCloudCreator	Creates a point cloud of specified size and density, with default component values.
PointCloudExpressionEvaluator	Evaluates expressions on each point in a point cloud feature, including algebraic operations and conditional statements, and sets individual point cloud component values.
PointCloudExtractor	Serializes the geometry of a point cloud feature into a Blob attribute, encoding the contents according to a choice of common binary point cloud formats.
PointCloudFilter	Separates point clouds into multiple features, based on evaluating expressions including component values, and creates a separate output port for each expression defined.
PointCloudMerger	Merges point clouds by joining points where selected component values match (join key), including x, y, z, and other components. Component values are transferred between point clouds and output is filtered based on matching success and duplication.
PointCloudOnRasterComponentSetter	Sets point cloud component values by overlaying a point cloud on a raster. The component values for each point are interpolated from band values at the point location.
PointCloudPropertyExtractor	Extracts the geometry properties of a point cloud feature and exposes them as attributes, optionally checking for their existence, retrieving component properties, and finding minimum and maximum values. Extents may also be recalculated and updated.
PointCloudReplacer	Decodes a binary attribute containing encoded point clouds stored as Blobs, replacing the feature’s geometry with the decoded point cloud.
PointCloudSimplifier	Reduces the number of points in a point cloud by selectively keeping points based on the shape of the point cloud. The simplified and removed points are output as two discrete point clouds.
PointCloudSorter	Sorts the points within a point cloud by one or more component values.
PointCloudSplitter	Separates point clouds into multiple features based on component values, color, or first/last return.
PointCloudStatisticsCalculator	Calculates statistics on point cloud components and adds the results as attributes.
PointCloudSurfaceBuilder	Takes an input point cloud and reconstructs it into an output mesh.
PointCloudThinner	Reduces the number of points in (thins) a point cloud by keeping points at a fixed interval, a maximum number of points, or a set quantity of first or last points. Remaining points are discarded.
PointCloudTransformationApplier	Applies a point cloud’s scale, offset, or transformation matrix to it, recalculating component values and removing the transformation values.

Configuration

Input Ports

Output Ports

Parameters

Sorting Components

This table specifies the components by which the point cloud will be sorted.

Sorting is done in the order specified. That is, all points will be sorted by the values of the first component in the list. If there are any ties, they will be broken by the values of the second component, then the third component, and so on.

Component

Specify a component for sorting.

The drop-down menu provides a list of standard component names. User-specified component names may be entered directly.

Order

Select the sort order:

Ascending
Descending

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.

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. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

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.

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

Transformers with table-style parameters have additional tools for populating and manipulating values.

Table Tools

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.

Reference

Processing Behavior	Feature-Based
Feature Holding	No
Dependencies	None
Aliases
History

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 PointCloudSorter on the FME Community.

Examples may contain information licensed under the Open Government Licence – Vancouver and/or the Open Government Licence – Canada.

Keywords: point "point cloud" cloud PointCloud LiDAR sonar