Physics Joints#
Overview#
This capability provides requirements for creating connections between rigid bodies in physics simulations. Joints constrain the relative motion between bodies, enabling complex mechanical systems and articulated structures.
Joints are fixed attachments that can represent the way a drawer is attached to a cabinet, a wheel to a car, or links of a robot to each other. A joint constrains the movement of rigid bodies and can be created between two rigid bodies or between one rigid body and world.
Mathematically, jointed assemblies can be modeled either in maximal (world space) or reduced (relative to other bodies) coordinates. An extension to the joint system based on reduced coordinates is provided with Articulations.
This capability is often paired with the Rigid Bodies capability to create comprehensive physics simulations.
Summary#
A UsdPhysicsJoint prim or one of its subtypes can be used to constrain two rigid bodies together, or to constrain a single rigid body to the World. This is achieved by setting the joint’s Body0 and Body1 relationship targets to either two rigid bodies or one to a rigid body and leaving the other one empty.
Any prim of the USD scene graph hierarchy may be marked with an UsdPhysicsArticulationRootAPI. This informs the simulation that any joints found in the subtree should preferentially be simulated using a reduced coordinate approach.
Schema / OpenUSD Specification#
Joints are created using the following schemas that are part of the core OpenUSD specification.
Requirements#
Tags |
Summary |
Compatibility |
Validator |
|---|---|---|---|
🔑 |
Rigid bodies which are not free floating should be connected using joints. |
openusd |
|
✅ |
openusd |
||
✅ |
Body0 and Body1 relationships must not have more than one target. |
openusd |
|
✅ |
openusd |
||
✅ |
openusd |
||
✅ |
openusd |
||
💎 |
For stable and fast simulations of kinematic chains, an asset should define an articulation. |
openusd |