(Scripting) Force update of physics scene?

Hi,

I am spawning multiple objects in a tight loop. The problem I am running into is that a ray cast from one object doesn't appear to see any of the objects created prior to it in the same loop.

Is there a way explicitly force the PhysicsScene to be updated during the loop?

EDIT: Note that the obvious, wait for the next fixedUpdate isn't an option as this is an Editor tool.

 

I mean in a loop I do this:

Spawn Object 1
Spawn Object 2 Above Object 1
Raycast down from Object 2. Ray does NOT see Object 1 like it should.

If those two actions take place as separate actions initiated by the user, thus allowing a FixedUpdate between them, then the ray sees the other object. If it happens in code during a loop, thus not allowing FixedUpdate to happen, the ray does NOT see the other object.

 

We are using the default scene.

 

3D. The raycast is performed using Physics.RaycastAll

 

I'll try to create a simple reproduction case.

 

Ok this does appear to work as expected in a simple test case, so I'm at a loss as to why it doesn't in the actual code. I will need to dig into it more

 

Hah got it. I works in a SIMPLE case, as in spawning the object and casting:

Code (CSharp):

1. m_child = (GamObject)PrefabUtility.InstantiatePrefab(childPrefab);
2. Vector3 direction = m_child.transform.position - transform.position;
3. RaycastHit[] hitInfos = Physics.RaycastAll(transform.position, direction, 100000f).ToArray();
4. Debug.Log(hitInfos.Length);  // Outputs 1

However, spawn the object and then change its parent before casting and it fails:

Code (CSharp):

1. m_child = (GamObject)PrefabUtility.InstantiatePrefab(childPrefab);
2. m_child.transform.SetParent(transform, false);
3. Vector3 direction = m_child.transform.position - transform.position;
4. RaycastHit[] hitInfos = Physics.RaycastAll(transform.position, direction, 100000f).ToArray();
5. Debug.Log(hitInfos.Length);  // Outputs 0

If I retrigger the spawn & cast, then it will see 1, then 2, etc in the debug log. So each run through it only sees the previous spawns, not the current one.

NOTE: I am drawing a DebugRay in the scene to visualize the Raycast so I can verify it is indeed pointing properly:

Code (CSharp):

1. Debug.DrawRay(transform.position, direction, Color.blue, 5f);

My guess here is that the collider is not updating immediately when the spawned object moves as a result of the parenting with worldPositionStays false.

 

I had tried done some testing with autoSyncTransforms but it was only a quick test as I wasn't sure it was a solution. Let m dig into that a bit more.

 

Many, Many thanks. Using Object.Instantiate does indeed seem to work.

EDIT: SyncTransforms also works but the impression I got was it should be more performant to do it with Instantiate

 

Don't ever close this thread, I run into this exact problem, and this helped me!

 

This fun little dive was while I was making this which was shown at SIGGRAPH last year

 

I switched to use Object.Instance it works!

 

Could this perhaps be added to the Raycast documentation? This cost me over a dozen hours of development time looking for solutions, workarounds, or known issue reports. Simply state that a ray will not hit an object that has moved until the next physics update, but that transforms can be synced manually with SyncTransforms(). I'm using raycasting to set up a puzzle, and the alternative do raycasting in Start is complex logic through several calls to FixedUpdate.