How to get the computed mass of a Collider in Bevy / Rapier3d?

Question

I have a Mesh with a ConvexDecomposition Collider using bevy_rapier3d.

How can I figure out the mass that rapier computes for this collider?

My code looks something like this:

fn asset_loaded(
    mut commands: Commands, 
    my_object: Query<(Entity, &Handle<Mesh>), With<MyObjectMarker>>,
    meshes: Res<Assets<Mesh>>,
    asset_server: Res<AssetServer>,
    loaded: Local<bool>,
){
     if *loaded{
         return;
     }
     let (my_entity, my_mesh) = my_object.single();
     if asset_server.load_state(my_mesh) != LoadState::Loaded {
         return;
     }
     let collider = Collider::from_bevy_mesh(
         meshes.get(my_mesh).unwrap(),
         &ComputedColliderShape::ConvexDecomposition(VHACDParameters::default()),
     ).unwrap();

     // ??: how can i get the computed mass of the object here? 

     commands.get_entity(my_entity).unwrap().insert(collider);
     *loaded = true;
}

Answer 1

You can use the function mass_properties like so:

// ??: how can i get the computed mass of the object here?
println!("{:#?}", collider.raw.mass_properties(1.0));

Note that you need to specify the density, if not done already. In the example above it is set to 1.

Answer 2

In case you want to handle the general case where you might have specified ColliderMassProperties, you could use the following:

fn query_object_mass(object: Query<&Collider, Option<&ColliderMassProperties>>) {
    let (collider, mass_properties) = object.single();
    let mass = match mass_properties {
        None => collider.raw.mass_properties(1.0).mass(),
        Some(ColliderMassProperties::Density(d)) => collider.raw.mass_properties(*d).mass(),
        Some(ColliderMassProperties::Mass(m)) => *m,
        Some(ColliderMassProperties::MassProperties(mp)) => mp.mass,
    }; 
}