Std Part

Description
Std Part (internally called App Part) is a general purpose container that keeps together a group of objects so that they can be moved together as a unit in the 3D view.

The Std Part element was developed to be the basic building block to create mechanical assemblies. In particular, it is meant to arrange objects that have a Part TopoShape, like Part Primitives, PartDesign Bodies, and other Part Features. The Std Part provides an Origin object with local X, Y, and Z axes, and standard planes; this Origin is used as reference to position and attach those other objects. In addition, Std Parts may be nested inside other Std Parts to create a full assembly from smaller sub-assemblies.

Although it is primarily intended for solid bodies, the Std Part can be used to manage any object that has a Placement property, so it can also contain Mesh Features, sketches, and other objects derived from App GeoFeature.

The Std Part tool is not defined by a particular workbench, but by the base system, thus it is found in the that is available in all workbenches.



How to use

 * 1) Press the  button. An empty Part is created and automatically becomes active.
 * 2) To add objects to a Part, select them in tree view, and then drag and drop them over the Part.
 * 3) To remove objects from a Part, drag them out of the Part, and onto the document label at the top of the tree view.

Properties
A Std Part is internally called App Part ( class), and is derived from an App GeoFeature ( class), therefore it shares most of the latter's properties.

In addition to the properties described in App GeoFeature, the App Part class has some properties that help it manage information in the context of an assembly, for example,, , , , , and.

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

 * : a description for this object. By default, it is an empty string.
 * : an identification or part number for this object. By default, it is an empty string.
 * : a field to specify the license for this object. By default, it is an empty string.
 * : a field to specify the web address to the license or contract for this object. By default, it is an empty string.
 * : a tuple of four floating point RGBA values to define the color of the object; by default it is, which is displayed as  on base 255, white color.
 * : 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.
 * : a list of referenced objects. By default, it is empty.

Hidden properties Data

 * : map with material properties. By default, it is empty.
 * : map with additional meta information. By default, it is empty.
 * : the universally unique identifier (UUID) (128-bit number) of the object. This is assigned at creation time.
 * : 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 list of expressions. By default, it is empty.
 * : whether to display the object or not.
 * : the App Origin object that is the positional reference for all elements listed in.
 * : whether the group is touched or not.

View
The App Part only has five of the properties of the basic App GeoFeature, and it does not have hidden properties.


 * : (default),, ,.
 * : (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.
 * : if it is, the object appears in the tree view. Otherwise, it is set as invisible.
 * : 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.
 * : 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.

Assembly concept
The Std Part is intended to be the basic building block to create assemblies. Unlike a PartDesign Body, an assembly is meant to be a collection of separate, distinguishable elements which are connected in some way in the physical world, for example, through pressure, screws, or glue.

Examples that could be Parts:
 * A wooden table that consists of individual wooden pieces (legs, top), which are put together by glue or metal screws.
 * A ball bearing that is composed of multiple steel balls, an inner ring, a separator or retainer, a seal or shield, and an outer ring.
 * An assembly of a screw with a washer, and a matching nut.



In general terms, when importing a STEP file into the program, the main assembly and its sub-assemblies will be imported as Part containers, each of them containing a simple Part Feature.

Active status
A document can contain multiple Parts but only one Part can be active at a time. An active Part will be displayed in the tree with a light blue background color.

Even when a Part is active, newly created objects are not placed inside the Part, but at the bottom of the tree view. Simply drag and drop them over the Part.

As of v0.19 it is unclear whether the Part's active status serves a real purpose.



Origin
The Origin consists of the three standard axes (X, Y, Z) and three standard planes (XY, XZ and YZ). Sketches can be attached to these planes. All elements inside the Part are referenced to the Part's Origin; which means that the Part can be moved and rotated in reference to the global coordinate system without affecting the placement of elements inside it.



Visibility Management
The Part's visibility supersedes the visibility of any object it contains. If the Part is hidden, the objects it contains will be hidden as well, even if their visibility is set to true. Multiple objects inside a Part can be visible at a time.

Limitations

 * At this time, Draft Snaps do not work on selected Part containers or on the objects inside of it.
 * A Part has no topological shape, therefore, it is not possible to apply most 3D operations such as Part Booleans on a Part itself, only on its contained objects.

Inheritance
A Std Part is formally an instance of the class, whose parent is the basic App GeoFeature ( class).



Scripting
FreeCAD Scripting Basics, and scripted objects.

See Part Feature for the general information on adding objects to the program.

A Std Part (App Part) is created with the method of the document. Once a Part exists, other objects can be added to it with the or  methods of this Part.