Accessing underlysing simulation and directly injecting entites there.

[stillonearth]

In my case I would need to load a URDF model with rapier_urdf and links, bodies and colliders to rapier instance of bevy_rapier only to sync transformation every step, avoiding injecting revy_rapier component to bevy entities.

What should I do in that case? Converting RapierCollider -> BevyCollider -> RapierCollider seems like a bad idea.

[stillonearth]

It turns out you just can

 mut q_rapier_context: Query<(
      Entity,
      &mut RapierRigidBodySet,
      &mut RapierContextColliders,
      &mut RapierContextJoints,
  )>,

[ThierryBerger]

bypassing bevy_rapier components

If I understand correctly, you want to bypass using bevy_rapier components to only synchronize their transforms:

bevy_rapier's transform synchronization from rapier to bevy is happening in

bevy_rapier/src/plugin/systems/rigid_body.rs

Line 403 in c5634a5

pub fn writeback_rigid_bodies(

As you can see it's quite tied to all those components, you may get away with copying only what you need, but be aware that's not a usecase much tested (see drawbacks).

using bevy_rapier components

If you want to create a bevy entity from an existing rapier rigidbody handle (from rapier_urdf).

So a counterpart to init_rigid_bodies, which takes a bevy entity and builds a rapier rigidbody (and init_joints and init_colliders...).

Drawbacks

Studying the above code might give information about how to achieve that, but adding external rigidbodies to bevy_rapier's internal rigidbody_set may lead to problems when despawning, changing their parameters or some getters...

Also, obviously other propagations from bevy to rapier will not work without additional effort.

Alternatives

• use rapier directly and provide your own minimal layer
• work on improving bevy_rapier to support that (support an addition to entity2[body, joints, collider])

[stillonearth]

I got an URDF body imported and simulated by bevy's rapier context, this way, but id doesn't collide bevy bevy spawned objects despite having right collider groups.

[ThierryBerger]

just checking, are these bodies on the same rapier context ? everything has colliders and they're not set to "sensor" ?

Maybe serialize the scene and share what you got :could help us help you. Or make a reproduction project so we can look at the same code :)

[stillonearth]

I got this solved, thanks. The issue was with not adjusting from rapier to bevy coordinate systems.