How to bake CollisionFilter?

Unity Engine
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1

Hi, unity teams :slight_smile:

I’m trying to use the following code to override CollisionFilter.GroupIndex at baking time. But I find that sometimes the GroupIndex is not what I expected.

It looks like that if two objects have same Collider shape / layer, they will share the same BlobAssetReference. So they can’t have different GroupIndex. Am I right? Is there any solution?

Thanks : D

        [WorldSystemFilter(WorldSystemFilterFlags.BakingSystem)]
        [UpdateInGroup(typeof(PostBakingSystemGroup))]
        private partial struct BakeSystem : ISystem
        {
            public void OnUpdate(ref SystemState state)
            {
                using var buffer = new EntityCommandBuffer(Allocator.Temp);
                foreach (var (@override, collider, e) in SystemAPI
                             .Query<PhysicsGroupIndexOverride, RefRW<PhysicsCollider>>()
                             .WithOptions(EntityQueryOptions.IncludePrefab).WithEntityAccess())
                {
                    var newCollider = collider.ValueRW.Value.Value.Clone();
                    var filter = newCollider.Value.GetCollisionFilter();
                    filter.GroupIndex = @override.GroupIndex;
                    newCollider.Value.SetCollisionFilter(filter);
                    collider.ValueRW.Value = newCollider;

                    buffer.RemoveComponent<PhysicsGroupIndexOverride>(e);
                }

                buffer.Playback(state.EntityManager);
            }
2

I found a similar question, but it seems only work at runtime.

3

Yes. If you need unique colliders per rigid body, just use the force unique option when baking, or PhysicsCollider.MakeUnique() at runtime.
See the collider documentation for more details.

4

thanks @daniel-holz :slight_smile:

for anyone else running into this problem, solution:
https://docs.unity3d.com/Packages/com.unity.physics@1.2/manual/physics-collider-components.html#making-colliders-unique-during-authoring

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