Compound Collision

Hi
I have a compound rigidbody and an array of all its colliders
NativeArray<CompoundCollider.ColliderBlobInstance> blobs;

After a sphereCast i have an array of hits and i also kept the array of all colliders in the compound rigidbody

now what i want to do is fairly simple, find out which collider exactly was hit
I have gotten as far as this

Code (CSharp):

1.  ChildCollider childCollider;
2. if (MyCompoundCollider.Value.GetLeaf(hit.ColliderKey, out childCollider))                      
3. {
4.      // WHAT DO I DO HERE?
5. }

Any tips?
Thanks!

 

childCollider.Collider gives you exactly the collider you hit. Is that what you need, or you somehow need more info?

 

well it has a collider pointer but what do i compare it against?

unsafe
{
childCollider.Collider == blobs.Collider.GetUnsafePtr() ?
}
its been awhile since i dealt with pointers in c#
i am trying to get the INDEX in the collider array eventually because i have some other data i need to access

 

Ah, if you need the index in the array you need to go through the array and compare each ColliderBlobInstance.Collider.GetUnsafePtr() to childCollider.Collider pointer, that will give you which one is hit. Although you probably want to mark your colliders as unique (force unique) to be sure it's not reused by multiple children.

I would advise something a bit more efficient, like storing collider pointers and indices in a map, to get more performant access.

Edit: your code in the unsafe block is exactly what you need for each array member.

 

This simple code does not work, these 2 colliders never match, could it be that they are not "unique" as you say?
the compound is made out of boxes

Code (csharp):

1.  for (int a = 0; a < fallingCompound.blobs.Length; ++a)
2.  {
3.       unsafe
4.        {
5.         if (childCollider.Collider == fallingCompound.blobs[a].Collider.GetUnsafePtr())
6.         {
7.               Debug.Log("collision found");
8.          }
9.        }
10.  }

 

Actually, scratch that, there is a simpler way. The hit.ColliderKey actually already contains index to the original array - just call PopSubKey() on it. The input argument to this function (numSubKeyBits) is actually stored in CompoundCollider.NumColliderKeyBits, just pass it in and you'll get your index as the out parameter...

 

Something like hit.ColliderKey.PopSubKey(MyCompoundCollider.Value.NumColliderKeyBits, out uint index) will do the trick.

 

it did!! thanks so much!

 

@argibaltzi If you donˋt mind - how did you get the array of colliders in the first place? Thanks!

 

i am using gameobjects and ecs together, so maybe that makes my life a little easier sometimes and sometimes not...


There are 2 ways i have access to them actually
1) i keep the original NativeArray<CompoundCollider.ColliderBlobInstance> blobs in a script
2) for compound colliders i have an empty gameobject(rigidbody) and all its colliders as children

Code (CSharp):

1.  
2.  
3. unsafe
4.             {
5.                 uint indexKey;
6.                 var isCompound = (CompoundCollider*)compoundDots.MyCollider.GetUnsafePtr();
7.                 if (hit.ColliderKey.PopSubKey(isCompound->NumColliderKeyBits, out indexKey))
8.                 {
9.                    outGameObject.transform.GetChild((int)indexKey); // this is the collider/gameobject of the compound
10.                 }
11.             }

i also have a scene dictionary to get back gameobjects once i know the entity
EntityToGameObjectTracker.Instance.EntityToGameobject.TryGetValue(hit.Entity, out outGameObject))

i use this for key entities/gameobjects that require tracking