Not getting CollisionEvent's from bevy_rapier2d

[aspiringLich]

Sorry if this isn't the right place to ask a question about bevy_rapier

Hello, I am trying to detect collision events with bevy_rapier2d and I cannot for the life of me figure out how to get them to work. Essentially what im trying to do is thus, i want to know whenever a marble (the small green thing) intersects with one of inputs / outputs (which dont generate contact forces but are sensors).

how im spawning the marble:

commands
    .spawn_atlas_sprite( // my own thing
        basic::marble_small,
        Color::GREEN,
        Transform::from_translation(pos - pos.z), // z-position: 0
    )
    .insert((
        Collider::ball(basic::marble_small.width() * 0.5),
        RigidBody::Dynamic,
        Velocity {
            linvel: transform.rotation.mul_vec3(Vec3::X).truncate() * 80.0,
            angvel: 0.0,
        },
        ColliderMassProperties::Mass(1.0),
        Restitution::coefficient(0.9),
    ))
    .insert(event.marble)
    .insert(Name::new("bit.marble"));

and how im spawning the input / output colliders:

let rotation = Quat::from_rotation_z(rotation);
let translation = rotation.mul_vec3(Vec3::X * offset) + Vec3::Z * z;
let transform = Transform {
    rotation,
    translation,
    scale: Vec3::ONE,
}

cmd.spawn((
      SpriteSheetBundle {
          texture_atlas,
          transform
          sprite: TextureAtlasSprite {
              index,
              color: Color::GRAY,
              anchor: Anchor::Center,
              ..default()
          },
          ..default()
      },
      Collider::ball(basic::marble_output.width() * 0.5),
      Sensor,
      marker::Output,
      Name::new("out.component"),
))

and the system for detecting the collision events (which definitely runs i didn't forget to put it in the schedule) (also this is just copied from the rapier docs):

fn display_events(
    mut collision_events: EventReader<CollisionEvent>,
    mut contact_force_events: EventReader<ContactForceEvent>,
) {
    for collision_event in collision_events.iter() {
        println!("Received collision event: {:?}", collision_event);
    }

    for contact_force_event in contact_force_events.iter() {
        println!("Received contact force event: {:?}", contact_force_event);
    }
}

ive tried setting their z-positions to be the same which i didn't think would matter (it didnt)

i know the obvious solution to detect collisions like this would be to have a system that checks each marble to see if its intersecting with each sensor but i hope theres a better solution.

thanks in advance 🙂

[rparrett]

From https://rapier.rs/docs/user_guides/bevy_plugin/advanced_collision_detection#collision-and-contact-force-events

Collision events (resp. contact force events) are only generated between two colliders if at least one of them has the ActiveEvents::COLLISION_EVENTS flag (resp. ActiveEvents::CONTACT_FORCE_EVENTS flags) in its active events.

The "flag" language is slightly confusing there, but you need to insert the ActiveEvents::COLLISION_EVENTS component onto the entities.

[aspiringLich]

Ah god I completely skimmed over that. That solved the problem thanks 👍