Draft PathArray

Description
The tool places copies of a selected shape along a selected path, which can be a Draft Wire, a Draft BSpline, and similar edges.

The PathArray tool can be used on 2D shapes created with the Draft Workbench, but can also be used on many types of 3D objects such as those created with the Part, PartDesign, or Arch Workbenches.

To position copies in an orthogonal array use Draft Array; to position copies at specified points use Draft PointArray; to create copies or clones, and manually place them use Draft Move, Draft Rotate, and Draft Clone.



Usage

 * 1) Select an object that you wish to distribute.
 * 2) Select a path object or some edges along which the object will be distributed.
 * 3) Press the  button.
 * 4) The Array object is immediately created. You must change the properties of the array to change the number and direction of copies created.

Each element in the array is an exact clone of the original object, but the entire array is considered a single unit in terms of properties and appearance.

The base object should be centred around the origin, even if the path starts somewhere else.

Options
There are no options for this tool. Either it works with the selected objects or not.

Properties

 * : specifies the object to duplicate in the path.
 * : specifies the path object.
 * : specifies the sub-elements (edges) of the path object. This property does not yet appear in the property editor.
 * : specifies the number of copies of the base object.
 * : if it is the copies are aligned to the path; otherwise they are left in their default orientation.
 * in certain cases the shape will appear flat, in reality it may have moved in the 3D space, so instead of using a flat view, change the view to axonometric.


 * : specifies a translation vector (x, y, z) to displace each copy along the path.
 * when is, the vector is relative to the local tangent, normal or binormal coordinates; otherwise the vector is relative to the global coordinates.

Scripting
Draft API and FreeCAD Scripting Basics.

The PathArray tool can be used in macros and from the Python console by using the following function:


 * Creates a object from the, by placing as many as  copies along.
 * If is given, it is a list of sub-objects of, and the copies are created along this shorter path.
 * If is given, it is a  that indicates an additional displacement to move the base point of the copies.
 * If is  the copies are aligned to the tangent, normal or binormal of the  at the point where the copy is placed.

Example:

Technical explanation for the Align property
When is, the placement of the copied shapes is easy to understand; they are just moved to a different position in their original orientation.

When is, the positioning of the shapes becomes a bit more complex:
 * 1) First, Frenet coordinate systems are built on the path: X is tangent, Z is normal, Y is binormal.
 * 2) Then the original object is copied to every on-path coordinate system, so that the global origin is matched with the on-path coordinate system origin.

The following images show how the array is produced, depending on which plane the path is.

Path on XY Plane:

Path on XZ Plane:

Path on YZ Plane:

As you reorient the path but not the object, the result is consistent: the object remains aligned to the path the way it was before reorienting the path.

thank you to user DeepSOIC for this explanation.

Additional alignment modes and options introduced in v0.19
Original mode (the default) is the historic alignment mode as in version 0.18. It is not really the Frenet alignment. Original mode uses the normal parameter from Draft.getNormal (or the default) as a constant - it does not calculate curve normal. X follows the curve tangent, Y is the normal parameter, Z is X.Cross(Y).

Tangent mode is similar to Original, but includes a rotation to align the Base object's X to the TangentVector before placing copies. After the rotation, Tangent behaves the same as Original. In previous versions this rotation would be performed manually before invoking PathArray.

Frenet mode orients the copies to a coordinate system along the path. X is tangent to curve, Y is curve normal, Z is curve binormal. If a normal can not be computed (ex a straight line), the default is used.

The ForceVertical option applies to Original and Tangent modes. When this option is applied, the normal parameter from Draft.getNormal is ignored. X follows the curve tangent, Z is the VerticalVector property and Y is X.Cross(Z).

Version 18 cycle chain - Original mode

Railway cross ties (sleepers) - Tangent mode + ForceVertical

Frenet Mode