Affiner

Categories

Coordinates

Performs an affine transformation on the coordinates of the feature.

An affine transformation preserves lines and parallelism in geometry. That is, any lines that were parallel before the transformation are parallel after the transformation. In addition, if a number of points falling on a straight line are transformed, the resulting coordinates will fall on a straight line in the new coordinate system.

Affine transformations include translations, rotations, scalings, and reflections.

Input Ports

This transformer accepts all features. Arcs and ellipses are preserved.

Output Ports

The transformed features.

The dynamic <Rejected> port appears when a parameter is set to a non-literal value that might make processing impossible.

For example, if a numeric parameter such as Line Width, Count Start, or Decimal Places is set to an expression, attribute value, or user parameter, it is possible to pass in a non-numeric value that cannot be used. Decimal Places = Cat cannot be processed, so the feature will be output via this port.

Rejected features will have an fme_rejection_code attribute explaining the reason for rejection.

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

Coefficients

To use the Affiner, you need to provide the 6 parameters that drive the following affine transform equation:

x' = Ax + By + C

y' = Dx + Ey + F

Where (x,y) is the input point and (x',y') is the transformed output point.

Examples

Translating Features East and North

To move features 500 units east and 1000 units north, use the following formula:

x' = 1x + 0y + Easting

y' = 0x + 1y + Northing

 

x' = 1x + 0y + 500

x' = 1x + 0y + 500

You would then enter the corresponding values for A to F in the Affiner parameters (for example, A=1, B=0, C=500, D=0, E=1, F=1000)

Scaling a Feature Set

To scale features by factor R, use the scale factor to the X and Y terms as follows:

x' = Rx + 0y + 0

y' = 0x + Ry + 0

To increase the scale by 10 times:

x' = 10x + 0y + 0

y' = 0x + 10y + 0

Rotating Features

To rotate features, apply the appropriate cos and sin functions associated with the rotation angle to the X,Y coefficients:

x' = cos(w)x + -sin(w)y + 0

y' = sin(w)x + cos(w)y + 0

where w = angle of rotation.

So, for a rotation of 30 degrees, cos(30) = 0.866025, sin(30) = 0.5, you would use:

x' = 0.866025*x + -0.5*y + 0

y' = 0.5*x + 0.866025*y + 0

to rotate a set of features by 30 degrees.

Combining Transformations

You can combine a set of transformations into one formula, or perform them in series to make it easier to debug or edit. For example, it may be easier to do your rotation and then scaling in two different Affiner transformers rather than trying to combine them into one transformation. Naturally, one advantage to doing it all in one transformation would be speed.

Note: Right-click on the transformer in the workspace and click Show Summary Annotation. This makes it easy to preview the transformation formula that will be used.

Usage Notes

  • Use the Affiner, rather than the Scaler, when scaling rasters. Because raster data is scaled around the data origin, not the coordinate origin, using the Scaler can cause an unexpected data shift).

Related Transformers

  • Please also see the AffineWarper, which performs warping operations on the spatial coordinates of features. The AffineWarper is used to adjust a set of observed features so they more closely match some set of reference features.
  • The Scaler and Offsetter are both simplified versions of the Affiner. For example:

x' = Ax + By + C

and

y' = Dx + Ey + F

where A = 1000 and E = 1000

In this case, x' = 1000x and y' = 1000y is the same as Scaler.

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.

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.

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.

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.

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 samples and information about this transformer on the FME Community.

 

Keywords: pointcloud