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Grouping And Parenting Objects

There can be many objects in a scene: A typical stage scene consists of furniture, props, lights, and backdrops. Blender helps you keep everything organized by allowing you to group like objects together.

When modeling a complex object, such as a watch, you may choose to model the different parts as separate objects. However, all of the parts may be attached to each other. In these cases, you want to designate one object as the parent of all the children. Movement and rotation of the parent also affects the children.

Parenting objects

To parent objects, select at least two objects (Select the child objects first, and select the parent object last), and press CtrlP. A confirmation dialog will pop up asking Make Parent. Selecting Make Parent confirms and the child/children to parent relationship is created. The last object selected will be the active object (outlined in yellow), and will also be the parent object. If you selected multiple objects before selecting the parent, they will all be children of the parent and will be at the same level of the hierarchy (they are “siblings”).

For non-inverse-mode press ⇧ ShiftCtrlP instead. This creates an alternative parent-child-relationship where child-objects exist entirely in parent coordinate system. This is the better choice for CAD purposes for example.

Moving and rotating the parent will also usually move/rotate the child/children. However moving/rotating the child/children of the parent, will not result in the parent moving/rotating. In other words, influence is usually descendant (parent → child/children), and not ascendant (child/children → parent).

Vertex Parent

You can parent an object to a single vertex or a group of three vertices as well; that way the child/children will move when the parent mesh is deformed, like a mosquito on a pulsing artery. In Object mode, select the child/children and then the parent object. ⇆ Tab into Edit mode and on the parent object select either one vertex that defines a single point, or select three vertices that define an area (the three vertices do not have to form a complete face they can be any three vertices of the parent object), and then hit CtrlP and confirm.

At this point if a single vertex was selected a relationship/parenting line will be drawn from the vertex to the child/children. If three vertices were selected then a relationship/parenting line is drawn from the averaged center of the three points (of the parent object) to the child/children. Now, as the parent mesh deforms and the chosen parent vertex/vertices move, the child/children will move as well.

Note It is in fact a sort of “reversed” hook

Options

Move child

You can move a child object to its parent by clearing its origin. The relationship between the parent and child isn’t affected. Select the child object and press AltO. By confirming the dialog the child object will snap to the parent’s location. Use the Outliner view to verify that the child object is still parented.

Remove relationship/Clear Parent

You can remove a parent-child relationship via AltP

The menu contains:

Clear Parent

If the parent in the group is selected nothing is done. If a child or children are selected they are disassociated with the parent, or freed, and they return to their original location, rotation, and size.

Clear and Keep Transformation

Frees the children from the parent, and keeps the location, rotation, and size given to them by the parent.

Clear Parent Inverse

Places the children with respect to the parent as if they were placed in the Global reference. This effectively clears the parent’s transformation from the children. For example, if the parent is moved 10 units along the X axis and Clear Parent Inverse is invoked, any selected children are freed and moved -10 units back along the X axis. The “Inverse” only uses the last transformation; if the parent moved twice, 10 units each time for a total of 20 units, then the “Inverse” will only move the child back 10 units, not 20.

Parenting Example

The active object, in yellow (cube A), will be made the parent of all the other object(s) in the group (orange cube B). The center(s) of all children object(s) are now linked to the center of the parent by a dashed line; see image (Parenting Example). The parent object is cube “A” and the child object is cube “B”. The link is labeled “L”.

At this point, grabbing, rotating, and scaling transformations to the parent will do the same to the children. Parenting is a very important tool with many advanced applications, as we’ll see in later chapters; it is used extensively with advanced animations.

Hints

There is another way to see the parent-child relationship in groups and that is to use the Outliner view of the Outliner window. Image (Outliner view) is an example of what the Outliner view looks like for the (Parenting Example). Cube “A”’s object name is “Cube_Parent” and cube “B” is “Cube_Child”.

Separating Objects

At some point, you’ll come to a time when you need to cut parts away from a mesh to be separate. Well, the operation is easy.

To separate an object, the vertices (or faces) must be selected and then separated, though there are several different ways to do this. In Edit Mode, press P then select one of the following.

Options

Selected

This option separates the selection to a new object.

All Loose Parts

Separates the mesh in its unconnected parts.

By Material

Creates separate mesh objects for each material.

Grouping objects

Group objects together without any kind of transformation relationship. Use groups to just logically organize your scene, or to facilitate one-step appending or linking between files or across scenes. Objects that are part of a group always shows as light green when selected; see image (Grouped objects).

Options

Creating a Group

CtrlG creates a new group and adds the selected object(s) to it.

Naming a Group

All groups that an objects have been assigned to are listed in the Object Properties Panel's Relations panel. To rename a group, simply click in the groups name field.

To name groups in the Outliner window, select Groups as the outliner display from the header combo box, and CtrlLMB click on the group name. The name will change to an editable field; make your changes and press ↵ Enter.

Restricting Group Contents via Layers

The cluster of layer buttons attached to each group determines from which layers the group objects will be included when duplicated. If your group contains objects on layers 10, 11 and 12, but you disable the layer 12 button in the group controls, duplicates of that group (using the Dupligroup feature) will only show the portions of the group that reside in layers 10 and 11.

Appending or Linking Groups

To append a group from another .blend file, consult this page. In summary, File → Append or Link → filename → Group → groupname.

Select Grouped

⇧ ShiftG pops up a dialog for selecting objects based on parenting and grouping characteristics.

Options

Children

Selects all the active object’s children, and the children’s children, up to the last generation.

Immediate Children

Selects all the active object’s children, but not those of these children (no “grandchildren” selected.)

Parent

Selects the parent of the active object and deselects the active object.

Siblings

Selects all the siblings of the active object.

Type

Selects objects based on the current active object type.

Layer

Selects all objects on the same layer(s) of the active object.

Group

Selects objects that belong to the same group as the active object.

Hook

Selects all hooks which are attached to the active object.

Pass

Selects all objects which have the same PassIndex number as the active object. See the ID Mask node usage for more information on this option.

Color

Selects objects that have the same color (the one set in Draw panel) as the active object.

Properties

Selects objects that have the same game properties as the active object.