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rigid_body_velocity

The velocity of a dynamic rigid-body controls how fast it is moving in time. The velocity is applied at the center-of-mass of the rigid-body, and is composed of two independent parts:

  1. The linear velocity is specified as a vector representing the direction and magnitude of the movement.
  2. In 3D, the angular velocity is given as a vector representing the rotation axis multiplied by the rotation angular speed in rad/s (axis-angle representation). In 2D, the angular velocity is given as a real representing the angular speed in rad/s.
info

The velocity is only relevant to dynamic rigid-bodies. It has no effect on fixed rigid-bodies, and the velocity of kinematic rigid-bodies are automatically computed at each timestep based on their next kinematic positions.

The velocity of a rigid-body is automatically updated by the physics pipeline after taking forces, contacts, and joints into account. It can be set when the rigid-body is created or after its creation:

/* Set the velocities when the rigid-body is created. */
let rigid_body = RigidBodyBuilder::dynamic()
    // The linear velocity of this body.
    // Default: zero velocity.
    .linvel(Vector::new(1.0, 3.0))
    // The angular velocity of this body.
    // Default: zero velocity.
    .angvel(3.0)
    // All done, actually build the rigid-body.
    .build();
/* Set the velocities after the rigid-body creation. */
let rigid_body = &mut world.bodies[rigid_body_handle];
// The `true` argument makes sure the rigid-body is awake.
rigid_body.set_linvel(Vector::new(1.0, 3.0), true);
rigid_body.set_angvel(3.0, true);
assert_eq!(rigid_body.linvel(), Vector::new(1.0, 3.0));
assert_eq!(rigid_body.angvel(), 3.0);
 
/* Set the velocities when the rigid-body is created. */
commands.spawn(RigidBody::Dynamic).insert(Velocity {
    linear: Vec2::new(0.0, 2.0),
    angular: 0.4,
});
/* Set the velocities inside of a system. */
fn modify_body_velocity(mut velocities: Query<&mut Velocity>) {
    for mut vel in velocities.iter_mut() {
        vel.linear = Vec2::new(0.0, 2.0);
        vel.angular = 0.4;
    }
}
 
/* Set the velocities when the rigid-body is created. */
let rigidBodyDesc = RAPIER.RigidBodyDesc.dynamic()
    // The linear velocity of this body.
    // Default: zero velocity.
    .setLinvel(1.0, 3.0)
    // The angular velocity of this body.
    // Default: zero velocity.
    .setAngvel(3.0);
let rigidBody = world.createRigidBody(rigidBodyDesc);
/* Set the velocities after the rigid-body creation. */
// The `true` argument makes sure the rigid-body is awake.
rigidBody.setLinvel({ x: 1.0, y: 3.0 }, true);
rigidBody.setAngvel(3.0, true);
 
/* Set the velocities when the rigid-body is created. */
R2RigidBodyDesc rigid_body = r2DynamicRigidBodyDesc();
// The linear velocity of this body.
// Default: zero velocity.
rigid_body.linvel = r2Vector(1.0, 3.0);
// The angular velocity of this body.
// Default: zero velocity.
rigid_body.angvel = 3.0;
/* Set the velocities after the rigid-body creation. */
// The last `1` argument makes sure the rigid-body is awake.
r2RigidBody_SetLinvel(rigid_body_handle, r2Vector(1.0, 3.0), 1);
r2RigidBody_SetAngvel(rigid_body_handle, 3.0, 1);
R2Vector linvel = r2RigidBody_Linvel(rigid_body_handle);
assert(linvel.x == 1.0 && linvel.y == 3.0);
assert(r2RigidBody_Angvel(rigid_body_handle) == 3.0);
 
# Set the velocities when the rigid-body is created.
rigid_body = (
    rp.RigidBody.dynamic()
    # The linear velocity of this body.
    # Default: zero velocity.
    .linvel((1.0, 3.0, 4.0))
    # The angular velocity of this body.
    # Default: zero velocity.
    .angvel((3.0, 0.0, 0.0))
    # All done, actually build the rigid-body.
    .build()
)
# Set the velocities after the rigid-body creation.
rigid_body = world.rigid_bodies[rigid_body_handle]
# Setting these properties automatically wakes the rigid-body up.
rigid_body.linvel = (1.0, 3.0, 4.0)
rigid_body.angvel = (3.0, 0.0, 0.0)
assert rigid_body.linvel == rp.Vec3(1.0, 3.0, 4.0)
assert rigid_body.angvel == rp.Vec3(3.0, 0.0, 0.0)

Alternatively, the velocity of a dynamic rigid-body can be altered indirectly by applying a force or an impulse.