Part Feature/en

Introduction


A Part Feature object, or formally a, is a simple element with a topological shape associated to it that can be displayed in the 3D view.

A Part Feauture is the parent class of most 2D (Draft, Sketcher) and 3D (Part, PartDesign) objects, with the exception of meshes, which are normally based on Mesh Feature, or Fem FemMeshObject for FEM objects.

Every object created with the Part Workbench is essentially a Part Feature.



Usage
The Part Feature is an internal object, so it cannot be created from the graphical interface, only from the Python console as described in the Scripting section.

The is defined in the Part Workbench but can be used as the base class for scripted objects in all workbenches that produce 2D and 3D geometrical shapes. Essentially all objects produced in the Part Workbench are instances of a. Solid objects imported from STEP or BREP files will be imported using the Part Workbench, so they will also be imported as elements albeit without parametric history.

is also the parent class of the PartDesign Body, of the PartDesign Features, and of the Part Part2DObject, which is specialized for 2D (planar) shapes.

A has simple properties like a placement, and visual properties to define the appearance of its vertices, edges, and faces. Workbenches can add more properties to this basic element to produce an object with complex behavior.

Properties
A Part Feature ( class) is derived from the basic App GeoFeature ( class), therefore it shares all the latter's properties.

In addition to the properties described in App GeoFeature, the Part Feature has the property, which stores the Part TopoShape of this object; this is the geometry that is shown in the 3D view.

Other properties that this object has are those related to the appearance of its TopoShape, including, , , , , , , , and also the hidden properties , , , , and.

See Property for all property types that scripted objects can have.

These are the properties available in the property editor. Hidden properties can be shown by using the command in the context menu of the property editor.

Data

 * : the position of the object in the 3D view. The placement is defined by a point (vector), and a  (axis and angle). See Placement.
 * : the angle of rotation around the . By default, it is (zero degrees).
 * : the unit vector that defines the axis of rotation for the placement. Each component is a floating point value between and . If any value is above, the vector is normalized so that the magnitude of the vector is . By default, it is the positive Z axis,.
 * : a vector with the 3D coordinates of the base point. By default, it is the origin.
 * : the user editable name of this object, it is an arbitrary UTF8 string.

Hidden properties Data

 * : a list of expressions. By default, it is empty.
 * : a longer, user editable description of this object, it is an arbitrary UTF8 string that may include newlines. By default, it is an empty string.
 * : a custom class associated with this object. This only exists for the Python version. See Scripting.
 * : a Part TopoShape class associated with this object.
 * : whether to display the object or not.

View
Most objects in FreeCAD have what is called a "view provider", which is a class that defines the visual appearance of the object in the 3D view, and in the tree view. The default view provider of Part Feature objects defines the following properties. Scripted objects that are derived from Part Feature will have access to these properties as well.


 * : it is a companion to . It is another way to specify how finely to generate the mesh for rendering on screen or when exporting. The default value is, or . This is the maximum value, the smaller the value the smoother the appearance will be in the 3D view, and the finer the mesh that will be exported.
 * : if it is, the object will show the bounding box in the 3D view.
 * : it is a companion to . It is another way to specify how finely to generate the mesh for rendering on screen or when exporting. The default value is . This is the maximum value, the smaller the value the smoother the appearance will be in the 3D view, and the finer the mesh that will be exported.

The deviation is a value in percentage that is related to the dimensions in millimeters of the bounding box of the object. The deviation in millimeters can be calculated as follows:

where, , are the bounding box dimensions.


 * : (regular visualization),  (no edges),  (no faces),  (only vertices).
 * : (default),, , ; defines the style of the edges in the 3D view.
 * : (default), ; the illumination comes from two sides or one side in the 3D view.
 * : a tuple of three floating point RGB values to define the color of the edges in the 3D view; by default it is, which is displayed as  on base 255, almost black.
 * : a float that determines the width in pixels of the edges in the 3D view. It defaults to.
 * : (default),, ,.
 * : similar to, defines the color of the vertices.
 * : similar to, defines the size of the vertices.
 * : if it is, the object can be picked with the pointer in the 3D view. Otherwise, the object cannot be selected until this option is set to.
 * : (default), . If the option is, the entire shape (vertices, edges, and faces) will be highlighted in the 3D view; if it is  only the bounding box will be highlighted.
 * : similar to, defines the color of the faces. It defaults to , which is displayed as on base 255, a light gray.
 * : if it is, the object appears in the tree view. Otherwise, it is set as invisible.
 * : an integer from to  (a percentage) that determines the level of transparency of the faces in the 3D view. A value of  indicates completely invisible faces; the faces are invisible but they can still be picked as long as  is.
 * : if it is, the object appears in the 3D view; otherwise it is invisible. By default this property can be toggled on and off by pressing the bar in the keyboard.

Hidden properties View

 * : it is a list of RGB tuples defining colors, similar to . It defaults to a list of one.
 * : it is a list of RGB tuples defining colors, similar to . It defaults to a list of one.
 * : an App Material associated with the edges in this object. By default it is empty.
 * : it is a list of RGB tuples defining colors, similar to . It defaults to a list of one.
 * : an App Material associated with the vertices in this object. By default it is empty.
 * : a custom view provider class associated with this object. This only exists for the Python version. See Scripting.
 * : an App Material associated with this object. By default it is empty.

Deviation value


See the forum thread, Deviation and Angular deflection.

Scripting
FreeCAD Scripting Basics, and scripted objects.

A Part Feature is created with the method of the document.

This basic doesn't have a Proxy object so it can't be fully used for sub-classing.

Therefore, for Python subclassing, you should create the object.

Name
The function has two basic string arguments.


 * The first argument indicates the type of object, in this case,.
 * The second argument is a string that defines the attribute. If it is not provided, it defaults to the same name as the class, that is,.
 * The can only include simple alphanumeric characters, and the underscore, . If other symbols are given, these will be converted to underscores; for example,  is converted to.
 * The cannot start with a number; it must start with a letter or the underscore, . For example,  is converted to.
 * The is fixed at creation time; it cannot be modified afterwards.
 * The must be unique in the entire document. If the same  is used at creation time with many objects, a sequential number will be appended automatically so that the resulting names are unique; for example, if  already exists, then new objects will be called, , , etc.

Label
If desired, the attribute can be changed to a more meaningful text.
 * Upon creating the object, the is the same as the.
 * However, unlike the, the can accept any UTF8 string, including accents and spaces. Since the tree view displays the , it is a good practice to change the  to a more descriptive string.
 * By default the is unique, just like the . However, this behavior can be changed in the preferences editor, . This means that in general the  may be repeated in the same document; when testing for a specific element the user should rely on the  rather than on the.