rigid_body_gravity

Gravity is such a common force that it is implemented as a special case (even if it could easily be implemented by the user using force application). The gravity is given by the field PhysicsWorld::gravity (or as an argument to the PhysicsPipeline::step method) and can be modified at will.The gravity is given by the field RapierConfiguration::gravity of the component RapierConfiguration and can be modified at will.The gravity is given to the constructor of the physics World. It can be modified by modifying the field World.gravity. The gravity is set with r3SetGravity (and read with r3Gravity) and can be modified at will.The gravity is given by the PhysicsWorld.gravity property (initialized by the gravity argument of the PhysicsWorld constructor, and zero by default) or as an argument to the PhysicsPipeline.step method, and can be modified at will. Note however that a change of gravity won't automatically wake-up the sleeping bodies so keep in mind that you may want to wake them up manually before a gravity change. They can all be woken up at once with PhysicsWorld.wake_up_all.

note

Because fixed and kinematic bodies are immune to forces, they are not affected by gravity.

info

A rigid-body with no mass will not be affected by gravity either. So if your rigid-body doesn't fall when you expected it to, make sure it has a mass set explicitly, or has at least one collider with non-zero density attached to it.

It is possible to change the way gravity affects a specific rigid-body by setting the rigid-body's gravity scale to a value other than 1.0. The magnitude of the gravity applied to this body will be multiplied by this scaling factor. Therefore, a gravity scale set to 0.0 will disable gravity for the rigid-body whereas a gravity scale set to 2.0 will make it twice as strong. A negative value will flip the direction of the gravity for this rigid-body.

This gravity scale factor can be set when the rigid-body is created or after its creation:

/* Set the gravity scale when the rigid-body is created. */
let rigid_body = RigidBodyBuilder::dynamic()
    // Divide by 2 the strength of gravity for this rigid-body.
    .gravity_scale(0.5)
    .build();

/* Set the gravity scale 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_gravity_scale(0.5, true);
assert_eq!(rigid_body.gravity_scale(), 0.5);

/* Set the gravity scale when the rigid-body is created. */
commands.spawn(RigidBody::Dynamic).insert(GravityScale(2.0));

/* Set the gravity scale inside of a system. */
fn modify_body_gravity_scale(mut grav_scale: Query<&mut GravityScale>) {
    for mut grav_scale in grav_scale.iter_mut() {
        grav_scale.0 = 2.0;
    }
}

/* Set the gravity scale when the rigid-body is created. */
let rigidBodyDesc = RAPIER.RigidBodyDesc.dynamic()
    .setGravityScale(2.0);
let rigidBody = world.createRigidBody(rigidBodyDesc);

/* Set the gravity scale after the rigid-body creation. */
rigidBody.setGravityScale(2.0, true);

/* Set the gravity scale when the rigid-body is created. */
R2RigidBodyDesc rigid_body = r2DynamicRigidBodyDesc();
// Divide by 2 the strength of gravity for this rigid-body.
rigid_body.gravityScale = 0.5;

/* Set the gravity scale after the rigid-body creation. */
// The last `1` argument makes sure the rigid-body is awake.
r2RigidBody_SetGravityScale(rigid_body_handle, 0.5, 1);
assert(r2RigidBody_GravityScale(rigid_body_handle) == 0.5);

# Set the gravity scale when the rigid-body is created.
rigid_body = (
    rp.RigidBody.dynamic()
    # Divide by 2 the strength of gravity for this rigid-body.
    .gravity_scale(0.5)
    .build()
)

# Set the gravity scale after the rigid-body creation.
rigid_body = world.rigid_bodies[rigid_body_handle]
# Setting this property automatically wakes the rigid-body up.
rigid_body.gravity_scale = 0.5
assert rigid_body.gravity_scale == 0.5