Articulation Body component reference
Switch to ScriptingArticulation Bodies enable you to build physics articulations such as robotic arms or kinematic chains with GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary that are hierarchically organized. They help you get realistic physics behaviors in the context of simulation for industrial applications.
Properties
An Articulation Body allows you to define in one single component the properties that you would similarly define through a RigidBodyA component that allows a GameObject to be affected by simulated gravity and other forces. More info
See in Glossary and a regular Joint in a classic configuration. That said, these properties depend on the GameObject position in the hierarchy:
- For the root GameObject of the articulation, you can only set up physical body properties:
- For any child GameObject within the articulation, you can set up physical body properties as well as the type and properties of the jointA physics component allowing a dynamic connection between Rigidbody components, usually allowing some degree of movement such as a hinge. More info
See in Glossary that links this GameObject to its parent GameObject:
The Articulation Body properties fall into the following main categories:
Physical body properties
Define the way the Articulation Body responds to the physics environment.
| Property | Description |
|---|---|
| Mass | The mass of the Articulation Body (in kilograms by default). |
| Immovable | Use this property to define whether this articulation body is movable or not. You can set this property only for the root Articulation Body. This property is useful to make the base body of robotic hands immovable, for example. The physics engineA system that simulates aspects of physical systems so that objects can accelerate correctly and be affected by collisions, gravity and other forces. More info See in Glossary solves it separately from all the other constraints and guarantees that it is not violated. |
| Use Gravity | Use this property to make the gravity affect this Articulation Body or not. |
Joint anchor properties
Define the coordinates of the joint anchors for the Articulation Body and its parent Articulation Body.
| Property | Description |
|---|---|
| Compute Parent Anchor | Enable this property to make the parent-relative anchor match the anchor of the current Articulation Body. If you disable this property, you can separately set values for Parent Anchor Position and Parent Anchor Rotation. |
| Anchor Position | The position coordinates of the Anchor, relative to the current Articulation Body. |
| Anchor Rotation | The rotation coordinates of the Anchor, relative to the current Articulation Body. |
| Parent Anchor Position | The position coordinates of the Parent Anchor, relative to the parent Articulation Body. This property only appears if you disable Compute Parent Anchor. |
| Parent Anchor Rotation | The rotation coordinates of the Parent Anchor, relative to the parent Articulation Body. This property only appears if you disable Compute Parent Anchor. |
| Snap Anchor to closest contact | Computes the point on the surface of this Articulation Body that is closest to the center of massRepresents the average position of all mass in a Rigidbody for the purposes of physics calculations. By default it is computed from all colliders belonging to the Rigidbody, but can be modified via script. More info See in Glossary of the parent Articulation Body, and sets the anchor to it. If Compute Parent Anchor is enabled, Unity also updates the parent anchor accordingly. |
Joint type selection and joint properties
Select the type of joint that links the current Articulation Body to its parent Articulation Body, and define its common and specific properties.
| Property | Description |
|---|---|
| Articulation Joint Type | The type of joint that connects this Articulation Body to its parent Articulation Body. Note: All types of joints have in common the properties that this table describes, and some of them have specific additional properties. Select from the following types:
|
| Linear Damping | Coefficient that controls the linear slow down. |
| Angular Damping | Coefficient that controls the rotational slow down. |
| Joint Friction | Coefficient that controls the energy loss caused by friction in the joint. |
Prismatic joint additional properties
| Property | Description |
|---|---|
| Axis | Specifies the axis that the prismatic joint allows motion along, relative to the parent anchor. |
| Motion | Specifies the motion restriction type along that axis:
|
| X Drive, Y Drive, or Z Drive | The properties of the linear drive that is attached to the joint, according to the selected Axis of the parent anchor. Note: There is only one Drive section here. Its title automatically adjusts according to the axis selection. |
Revolute joint additional properties
| Property | Description | |
|---|---|---|
| Motion | Specifies the rotation restriction type around the x-axis of the parent anchor.
|
|
| X Drive | The properties of the rotational drive that is attached to the joint, around the X axis of the parent anchor. |
Spherical joint additional properties
| Property | Description |
|---|---|
| Swing Y | Specifies the rotation restriction type around the Y axis:
|
| Swing Z | Specifies the rotation restriction type around the Z axis. The options are the same for all 3 axes. |
| Twist | Specifies the rotation restriction type around the X axis. The options are the same for all 3 axes. |
| Y Drive, Z Drive, and X Drive | The properties of the rotational drive that is attached to the joint, respectively around the Y, Z and X axes of the parent anchor. Note: There is a separate subsection for each drive. If you lock an axe, the InspectorA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info See in Glossary does not display its Drive properties. |
Joint drive properties
Set up joint limits about a specific axis, as well as the joint drive effect parameters for this axis.