Multiple collision bodies with different collision groups

[nikolajevs86]

Hi! Can somebody please help me with this example? I need to create two collision bodies with different collision group for the same NPC component, but I a bit stuck how to do it properly:

let mut npc = commands.spawn((
    NPC,
    RigidBody::KinematicPositionBased,
    Collider::ball(500.0),
    Ccd::disabled(),
    CollisionGroups::new(Group::GROUP_1, Group::GROUP_2),
));

npc.add_children(|entity| {
    entity.spawn((
        RigidBody::KinematicPositionBased,
        Collider::cuboid(50.0, 200.0),
        Ccd::disabled(),
        CollisionGroups::new(Group::GROUP_4, Group::GROUP_3),
    ));
});

It creates two bodies but, when I move my NPC then first body is properly attached and moved where it is needed, but the second one remains fixed on the scene and does not moves with the parent. Can someone share please what I am doing wrong?

[sebcrozet]

Hi! You need to add a TransformBundle to both the parent and child entities for transform propagation to work.

[nikolajevs86]

Adding TransformBundle::default() works, now collision body is not fixed any more, but it is placed not at the entity position but outside it and sometimes it even creates duplicate collision body, which is really weird

npc.add_children(|entity| {
    entity.spawn((            
        RigidBody::KinematicPositionBased,
        Collider::ball(500.0),
        Ccd::disabled(),
        CollisionGroups::new(Group::GROUP_1, Group::GROUP_2 | Group::GROUP_3),
        TransformBundle::default(),
    ));
});