Controls, Bones, and Nulls

The primary rig elements used when creating robust rigs in Control Rig are Controls, Bones, and Nulls. Each of these elements have wide-ranging applications and can be used together to create complete rigs.

This document provides an overview of Controls, Bones, and Nulls, and provides simple workflow examples for using them.

Prerequisites

• You have created and opened a Control Rig for a skeletal mesh.

Elements Overview

Controls, Bones, and Nulls are created by right-clicking in the Rig Hierarchy panel and selecting one of the options from the New menu.

By default, creating one of these elements will locate it at the origin (0,0,0) of the viewport. If you have an element selected in the Rig Hierarchy panel, it will instead create it at the location of, and parented to, that selected element. This makes it easy to align your elements with each other, using this selection context.

Organization

Elements can be renamed by right-clicking them in the Rig Hierarchy and selecting Rename or by pressing F2.

Elements can be re-organized by dragging them in the Rig Hierarchy.

• Dragging an element onto another element parents it to that element.

• Dragging an element to an empty region unparents it.

• Pressing Shift+P also unparents selected elements.

Controls

Controls are the main elements used for your Control Rig interaction. They are used to drive your Bone chains, animate in Sequencer, and provide additional custom attributes. You can also customize your Controls to have different shapes and colors, property types, and transform limits.

Creation Context

When creating Controls relative to a Bone, the Control will automatically inherit the same name as that Bone and apply _ctrl as a suffix.

Creating Multiple Controls

In addition to the normal creation method, you can also create Controls when multiple Bones are selected using a provided Python script. In the Rig Hierarchy, select multiple Bones, then right-click on them and select New > Add Controls For Selected. This will create Controls for all selected Bones, matching their names with the suffix _ctrl, and matching the hierarchy structure.

You can customize this creation method by holding Alt and clicking New > Add Controls For Selected. This will open a dialog window where you can customize the following settings:

Control Types

There are a variety of Control types that you can specify for Controls which provide alternative or more limited properties for it. This can be useful if you are wanting to create slider-based Controls, or Controls with simple attributes like Booleans.

You can specify the type of the Control by clicking the Control Type drop-down menu for a selected Control in the Details panel. The following Control types can be chosen:

For spatial Controls, such as Euler Transform, Rotator, Scale, and Position, there are additional transform-related features available to you in the details panel when viewing the Transform properties:

1. The Rotation drop-down menu is where you can select different rotation interpolation modes, such as Euler, Quaternion, or Axis and Angle.

2. Local /World Space buttons will swap the axis information displayed between local and world space. Shift-clicking will change all three axes.

3. Locks Scale, which will cause scaling to occur uniformly in each direction when changing scale.

Transform Limits

Spatial Controls can have limits placed on them so that they only can animate within a certain range. This can be useful if you are wanting to create slider or 2D-based controls and limit their movement range.

Limits are set on Controls by defining their minimum and maximum property ranges. You can locate these properties for a selected Control by clicking Min or Max under the Transform category in the Details panel.

Enable any axis channel to enable limits for that value, and define the number within the region next to it. In this example a Minimum limit of -50 and Maximum limit of 50 is set. Manipulating your Control will now keep its movement restricted to those limits.

Enable Draw Limits to visualize the limits of all Controls in the Viewport.

Bones

Separate from normal Bones that are included in your skeleton, new Bones can also be created in Control Rig. These Bones can be used in an auxiliary manner to provide extra Bones for specific rigging behavior, such as making ending effectors in an IK-chain, or making "dummy" Bones in order to control "real" Bones in a consolidated manner.

After creating a new Bone, you can move it in the viewport by entering into the Setup Event mode, which enables the ability to edit the Initial Pose of an element in the viewport. In the toolbar, click the Solve Direction drop-down menu and select Setup Event.

Once Setup Event is enabled, you can move your Bone in the viewport.

Workflow Example

In this example, a Bone created in Control Rig is being used as an end effector for a finger IK chain.

Nulls

Nulls are container elements used to collect, group, and transform other rig elements together in arbitrary ways. In a typical humanoid control rig setup, they can be used as a way to group your symmetrical controls, such as legs and arms, in order to mirror these controls. In this way, Nulls are a similar concept to Groups from Autodesk Maya, and are meant to be used for rigging organization.

By default, Nulls are not visible in the viewport. To view nulls, you can enable Display Nulls from the Viewport toolbar.

Similar to Bones, Nulls can be edited by enabling Setup Event from the Solve Direction dropdown menu. Once Setup Event is enabled, you can move your Null in the viewport.

Workflow Example

In this example, Nulls are being used to group several controls together along symmetrical and limb lines. This grouping can now facilitate easier organization, mirroring, and other rigging operations.

Transform Types

The position, rotation, and scale of rig elements are determined from multiple transform sources, which are named Initial, Current, and Offset. These transform types each perform transformations on rig elements at different phases of the Control Rig execution. You can view these different types from any selected rig element's details.

When a different Control type is specified for a Control, you can only specify Initial and Current Values.

Initial

Initial is the starting value of the element before control rig logic from the rig graph executes. It also specifies the default value of a rig element within its range of operation, and will affect the default value of Current.

You can edit the Initial value by either editing it from the Details panel, or by enabling Setup Event and manipulating the element in the Viewport, if it has a Transform.

Current

Current is the value of the element when operating in the Forwards Solve mode. It is meant to be the real-time actual transform of your Control, and manipulating Controls in the viewport will edit the Current pose. Within the Control rig editor, the Current pose is temporary and can be reset by recompiling or reopening the asset.

Offset Transform

Offset only appears for Controls with Control Type set to Euler Transform. It is used to spatially offset controls without changing the Initial or Current values, and provides the ability to change a Control's "zero position". In other rigging tools such as Autodesk Maya, Offset is analogous to Freeze Transformations, or Transform Offset Parent Matrix.