[DOTS] Adding / removing / disabling colliders to compound DynamicBody

Revised question in next post #1


Original question

I have followed Compound Demo, to create compound dynamic bodies.
EntityComponentSystemSamples/UnityPhysicsSamples/Assets/Tests/Compound/CompoundDemo.cs

I was playing about a bit with script, by adding cubic (5x5x5) cubes generation, which works fine.

Spoiler

Code (CSharp):

1. for ( int z = 0; z < i_count; z ++ )
2.             {
3.                 for ( int y = 0; y < i_count; y ++ )
4.                 {
5.                     for ( int x = 0; x < i_count; x ++ )
6.                     {
7.                         int i_index = z * i_count * i_count + y * i_count + x ;
8.                    
9.                         children [i_index] = new CompoundCollider.ColliderBlobInstance
10.                         {
11.                             CompoundFromChild = new RigidTransform(quaternion.identity, new float3( x, y, z )),
12.                             Collider = Unity.Physics.BoxCollider.Create(float3.zero, quaternion.identity, new float3(1), 0.05f)
13.                         } ;
14.                     }
15.                 }

Then followed Create method, using as reference point, to generate new compound body.

Code (CSharp):

1. BlobAssetReference<Unity.Physics.Collider> collider = CompoundCollider.Create(children);
2.             children.Dispose();
3.        
4.             CreateDynamicBody ( new float3(0, 1, 0), quaternion.identity, collider, float3.zero, float3.zero, 1.0f ) ;

From that point, how should I approach now, by amending this compound body, to be able adding, removing, or/and disabling certain amount of colliders?

If I look inside CreateDynamicBody, there is

Code (CSharp):

1. protected Entity CreateDynamicBody(float3 position, quaternion orientation, BlobAssetReference<Collider> collider,
2.         float3 linearVelocity, float3 angularVelocity, float mass)
3.     {
4.         return CreateBody ( position, orientation, collider, linearVelocity, angularVelocity, mass, true ) ;
5.     }

Which further leads to

Spoiler

Code (CSharp):

1. private Entity CreateBody(float3 position, quaternion orientation, BlobAssetReference<Collider> collider,
2.         float3 linearVelocity, float3 angularVelocity, float mass, bool isDynamic)
3.     {
4.         EntityManager entityManager = EntityManager;
5.  
6.         Entity entity = entityManager.CreateEntity(new ComponentType[] { });
7.  
8.         entityManager.AddComponentData(entity, new LocalToWorld { });
9.         entityManager.AddComponentData(entity, new Translation { Value = position });
10.         entityManager.AddComponentData(entity, new Rotation { Value = orientation });
11.  
12.         var colliderComponent = new PhysicsCollider { Value = collider };
13.         entityManager.AddComponentData(entity, colliderComponent);
14.  
15.         Mesh mesh = new Mesh();
16. #pragma warning disable 618
17.         List<Unity.Physics.Authoring.DisplayBodyColliders.DrawComponent.DisplayResult> meshes;
18.         unsafe { meshes = Unity.Physics.Authoring.DisplayBodyColliders.DrawComponent.BuildDebugDisplayMesh(colliderComponent.ColliderPtr); }
19. #pragma warning restore 618
20.         CombineInstance[] instances = new CombineInstance[meshes.Count];
21.         int numVertices = 0;
22.         for (int i = 0; i < meshes.Count; i++)
23.         {
24.             instances[i] = new CombineInstance
25.             {
26.                 mesh = meshes[i].Mesh,
27.                 transform = Matrix4x4.TRS(meshes[i].Position, meshes[i].Orientation, meshes[i].Scale)
28.             };
29.             numVertices += meshes[i].Mesh.vertexCount;
30.         }
31.         mesh.indexFormat = numVertices > UInt16.MaxValue ? UnityEngine.Rendering.IndexFormat.UInt32 : UnityEngine.Rendering.IndexFormat.UInt16;
32.         mesh.CombineMeshes(instances);
33.  
34.         entityManager.AddSharedComponentData(entity, new RenderMesh
35.         {
36.             mesh = mesh,
37.             material = isDynamic ? dynamicMaterial : staticMaterial
38.         });
39.  
40.         if (isDynamic)
41.         {
42.             entityManager.AddComponentData(entity, PhysicsMass.CreateDynamic(colliderComponent.MassProperties, mass));
43.  
44.             float3 angularVelocityLocal = math.mul(math.inverse(colliderComponent.MassProperties.MassDistribution.Transform.rot), angularVelocity);
45.             entityManager.AddComponentData(entity, new PhysicsVelocity()
46.             {
47.                 Linear = linearVelocity,
48.                 Angular = angularVelocityLocal
49.             });
50.             entityManager.AddComponentData(entity, new PhysicsDamping()
51.             {
52.                 Linear = 0.01f,
53.                 Angular = 0.05f
54.             });
55.         }
56.  
57.         return entity;
58.     }

I am able follow up to the

Code (CSharp):

1. var colliderComponent = new PhysicsCollider { Value = collider };
2.         entityManager.AddComponentData(entity, colliderComponent);

But from that point I am bit lost. I see pointer to the array of blocks to add inside colliderComponent. However, I ain't got clue, how to bite the problem, to modify script, so I can add extra / remove / disable some colliders to/from that compound.

I suppose, I could regenerate whole compound. But surely there is better approach.

Any thoughts?

 

With revision into problem, I looked a bit further into
EntityComponentSystemSamples/UnityPhysicsSamples/Assets/Common/Scripts/BasePhysicsDemo.cs
I understand that CombineMeshes allows to combine meshes into larger mesh.
I.e.

Code (CSharp):

1. mesh.CombineMeshes (instances);

It is used for example in example of compound colliders.
I did some basics tests
Unity 2019.2 DOTS Physics Test: 343k Compounds Cubes

My revised question would be, what is the opposite function to CombineMeshes, if I want to remove certain meshes / colliders from the compound? In other words, what would be opposite function of CompoundDemo
EntityComponentSystemSamples/UnityPhysicsSamples/Assets/Tests/Compound/CompoundDemo.cs
to disconnect / disjoint colliders?

My immediate thought would be, to look at mesh.subMeshCount (BasePhysicsDemo) from physics and then get relevant meshes somehow, based on vertices.

But I don't feel this is sufficient to resolve my compound colliders problem. Any thoughts?

 

I used the following systems to enable and disable colliders. Please let me if this approach has considerable flaws w.r.t performance.

Code (CSharp):

1. public struct PhysicsColliderHolder : IComponentData {
2.     public PhysicsCollider physicsCollider;
3. }
4.  
5. [UpdateInGroup(typeof(FixedStepSimulationSystemGroup))]
6. [UpdateAfter(typeof(EndFramePhysicsSystem))]
7. public class DisablePlayerTypeCollisionSystem : SystemBase {
8.     EntityCommandBufferSystem _entityCommandBufferSystem;
9.     protected override void OnCreate() {
10.         _entityCommandBufferSystem = World.GetOrCreateSystem<EndSimulationEntityCommandBufferSystem>();
11.     }
12.     protected override void OnUpdate() {
13.         var commandBuffer = _entityCommandBufferSystem.CreateCommandBuffer().AsParallelWriter();
14.         float deltaTime = Time.DeltaTime;
15.         Entities.
16.             ForEach((Entity entity, int entityInQueryIndex, in PhysicsCollider physicsCollider, in PlayerTypeData _, in ColliderTag __, in DisableRendering ____) => {
17.                 commandBuffer.RemoveComponent<PhysicsCollider>(entityInQueryIndex, entity);
18.                 commandBuffer.AddComponent<PhysicsColliderHolder>(entityInQueryIndex, entity, new PhysicsColliderHolder { physicsCollider = physicsCollider });
19.             }).ScheduleParallel();
20.         _entityCommandBufferSystem.AddJobHandleForProducer(Dependency);
21.     }
22. }
23.  
24.  
25.  
26.  
27. [UpdateInGroup(typeof(FixedStepSimulationSystemGroup))]
28. [UpdateAfter(typeof(EndFramePhysicsSystem))]
29. public class EnablePlayerTypeCollisionSystem : SystemBase {
30.     EntityCommandBufferSystem _entityCommandBufferSystem;
31.     protected override void OnCreate() {
32.         _entityCommandBufferSystem = World.GetOrCreateSystem<EndSimulationEntityCommandBufferSystem>();
33.     }
34.     protected override void OnUpdate() {
35.         var commandBuffer = _entityCommandBufferSystem.CreateCommandBuffer().AsParallelWriter();
36.         float deltaTime = Time.DeltaTime;
37.         Entities.
38.             WithNone<DisableRendering, PhysicsCollider>().
39.             ForEach((Entity entity, int entityInQueryIndex, in PhysicsColliderHolder physicsColliderHolder, in PlayerTypeData _, in ColliderTag __) => {
40.                 commandBuffer.AddComponent<PhysicsCollider>(entityInQueryIndex, entity, physicsColliderHolder.physicsCollider);
41.             }).ScheduleParallel();
42.         _entityCommandBufferSystem.AddJobHandleForProducer(Dependency);
43.     }
44. }