# Part Feature

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## Contents

A Part Feature object, or formally a Part::Feature, 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.

Simplified diagram of the relationships between the core objects in the program. The Part::Feature class is the origin of most 2D (Draft, Sketcher) and 3D (Part, PartDesign) objects that have a Part TopoShape.

## 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 Part::Feature 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 Part::Feature. Solid objects imported from STEP or BREP files will be imported using the Part Workbench, so they will also be imported as Part::Feature elements albeit without parametric history.

Part::Feature 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 Part::Feature 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 (Part::Feature class) is derived from the basic App GeoFeature (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 DataShape 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 ViewAngular Deflection, ViewDeviation, ViewDraw Style, ViewLighting, ViewLine Color, ViewLine Width, ViewPoint Color, ViewPoint Size, and also the hidden properties ViewDiffuse Color, ViewLine Color Array, ViewLine Material, ViewPoint Color Array, and ViewPoint Material.

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 Show all command in the context menu of the property editor.

### Data

Base

• DataPlacement (Placement): the position of the object in the 3D view. The placement is defined by a Base point (vector), and a Rotation (axis and angle). See Placement.
• DataAngle: the angle of rotation around the DataAxis. By default, it is 0° (zero degrees).
• DataAxis: the unit vector that defines the axis of rotation for the placement. Each component is a floating point value between 0 and 1. If any value is above 1, the vector is normalized so that the magnitude of the vector is 1. By default, it is the positive Z axis, (0, 0, 1).
• DataPosition: a vector with the 3D coordinates of the base point. By default, it is the origin (0, 0, 0).
• DataLabel (String): the user editable name of this object, it is an arbitrary UTF8 string.

#### Hidden properties Data

• Data (hidden)Expression Engine (ExpressionEngine): a list of expressions. By default, it is empty [].
• Data (hidden)Label2 (String): 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 "".
• Data (hidden)Proxy (PythonObject): a custom class associated with this object. This only exists for the Python version. See Scripting.
• Data (hidden)Shape (PartShape): a Part TopoShape class associated with this object.
• Data (hidden)Visibility (Bool): 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.

Base

• ViewAngular Deflection (Angle): it is a companion to ViewDeviation. It is another way to specify how finely to generate the mesh for rendering on screen or when exporting. The default value is 28.5 degrees, or 0.5 radians. 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.
• ViewBounding Box (Bool): if it is True, the object will show the bounding box in the 3D view.
• ViewDeviation (FloatConstraint): it is a companion to ViewAngular Deflection. It is another way to specify how finely to generate the mesh for rendering on screen or when exporting. The default value is 0.5%. 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:

deviation_in_mm = (w + h + d)/3 * deviation/100


where w, h, d are the bounding box dimensions.

• ViewDisplay Mode (Enumeration): Flat Lines (regular visualization), Shaded (no edges), Wireframe (no faces), Points (only vertices).
• ViewDraw Style (Enumeration): Solid (default), Dashed, Dotted, Dashdot; defines the style of the edges in the 3D view.
• ViewLighting (Enumeration): Two side (default), One side; the illumination comes from two sides or one side in the 3D view.
• ViewLine Color (Color): a tuple of three floating point RGB values (r,g,b) to define the color of the edges in the 3D view; by default it is (0.09, 0.09, 0.09), which is displayed as [25,25,25] on base 255, almost black .
• ViewLine Width (FloatConstraint): a float that determines the width in pixels of the edges in the 3D view. It defaults to 2.0.
• ViewOn Top When Selected (Enumeration): Disabled (default), Enabled, Object, Element.
• ViewPoint Color (Color): similar to ViewLine Color, defines the color of the vertices.
• ViewPoint Size (FloatConstraint): similar to ViewLine Width, defines the size of the vertices.
• ViewSelectable (Bool): if it is True, the object can be picked with the pointer in the 3D view. Otherwise, the object cannot be selected until this option is set to True.
• ViewSelection Style (Enumeration): Shape (default), BoundBox. If the option is Shape, the entire shape (vertices, edges, and faces) will be highlighted in the 3D view; if it is BoundBox only the bounding box will be highlighted.
• ViewShape Color (Color): similar to ViewLine Color, defines the color of the faces. It defaults to (0.8, 0.8, 0.8), which is displayed as [204,204,204] on base 255, a light gray.
• ViewShow In Tree (Bool): if it is True, the object appears in the tree view. Otherwise, it is set as invisible.
• ViewTransparency (Percent): an integer from 0 to 100 (a percentage) that determines the level of transparency of the faces in the 3D view. A value of 100 indicates completely invisible faces; the faces are invisible but they can still be picked as long as ViewSelectable is True.
• ViewVisibility (Bool): if it is True, the object appears in the 3D view; otherwise it is invisible. By default this property can be toggled on and off by pressing the Space bar in the keyboard.

#### Hidden properties View

• View (hidden)Diffuse Color (ColorList): it is a list of RGB tuples defining colors, similar to ViewShape Color. It defaults to a list of one [(0.8, 0.8, 0.8)].
• View (hidden)Line Color Array (ColorList): it is a list of RGB tuples defining colors, similar to ViewLine Color. It defaults to a list of one [(0.09, 0.09, 0.09)].
• View (hidden)Line Material (Material): an App Material associated with the edges in this object. By default it is empty.
• View (hidden)Point Color Array (ColorList): it is a list of RGB tuples defining colors, similar to ViewPoint Color. It defaults to a list of one [(0.09, 0.09, 0.09)].
• View (hidden)Point Material (Material): an App Material associated with the vertices in this object. By default it is empty.
• View (hidden)Proxy (PythonObject): a custom view provider class associated with this object. This only exists for the Python version. See Scripting.
• View (hidden)Shape Material (Material): an App Material associated with this object. By default it is empty.

### Deviation value

Deflection parameters of BRepMesh_IncrementalMesh algorithm; ${\displaystyle d<=}$ linear deflection, ${\displaystyle \alpha <=}$ angular deflection.

See the forum thread, Deviation and Angular deflection.

## Scripting

A Part Feature is created with the addObject() method of the document.

import FreeCAD as App

doc = App.newDocument()
obj.Label = "Custom label"


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

Therefore, for Python subclassing, you should create the Part::FeaturePython object.

import FreeCAD as App

doc = App.newDocument()
obj.Label = "Custom label"


### Name

The addObject function has two basic string arguments.

• The first argument indicates the type of object, in this case, "Part::FeaturePython".
• The second argument is a string that defines the Name attribute. If it is not provided, it defaults to the same name as the class, that is, "Part__FeaturePython".
• The Name can only include simple alphanumeric characters, and the underscore, [_0-9a-zA-Z]. If other symbols are given, these will be converted to underscores; for example, "A+B:C*" is converted to "A_B_C_".
• The Name cannot start with a number; it must start with a letter or the underscore, [_a-zA-Z]. For example, "123ABC" is converted to "_23ABC".
• The Name is fixed at creation time; it cannot be modified afterwards.
• The Name must be unique in the entire document. If the same "Name" 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 "Name" already exists, then new objects will be called "Name001", "Name002", "Name003", etc.

### Label

If desired, the Label attribute can be changed to a more meaningful text.

• Upon creating the object, the Label is the same as the Name.
• However, unlike the Name, the Label can accept any UTF8 string, including accents and spaces. Since the tree view displays the Label, it is a good practice to change the Label to a more descriptive string.
• By default the Label is unique, just like the Name. However, this behavior can be changed in the preferences editor, Edit → Preferences → General → Document → Allow duplicate object labels in one document. This means that in general the Label may be repeated in the same document; when testing for a specific element the user should rely on the Name rather than on the Label.