(18-03-2022, 08:21 AM)josemendez Wrote: Hi!

The contact list passed to OnCollision is the exact same one used internally by the engine to perform the actual simulation. What I mean by this is that if the particle exists in the scene and is colliding with stuff, then it must appear in the contact list. Internal collisions and collision callbacks aren't two separate systems.

How are you determining hand.SolverIndex? Is it _arm.elements[0].particle1? if so, note that this value is only available when the rope is already instantiated.

I assume you're doing something along the lines of hand.SolverIndex = _arm.elements[0].particle1 this at Start(), Awake(), OnEnable() or a similar event, so it may or may not return a correct value depending on the order in which game objects are instantiated, which as you know if undefined in Unity.

If my assumption is correct, you might want to wait for one frame after instantiating the rope to get the value of hand.SolverIndex.

(18-03-2022, 02:40 PM)VirtualCucumber Wrote: My only concern with this solution is that if the hand.SolverIndex was wrong then I would not be able to add force using Solver.externalForces[SolverIndex] in Hand.cs which works as seen in both gifs.

(18-03-2022, 02:40 PM)VirtualCucumber Wrote: No collision event gets fired at all but it still collides accurately with the cube collider.

(18-03-2022, 02:46 PM)josemendez Wrote: Thats' simply not possible, since the collision events contain the exact same data used for collision response. The engine reports the contacts that it has solved. If the particle is colliding, there must exist a contact against it in the contact list.

(18-03-2022, 02:46 PM)josemendez Wrote: Do any of the ropes in your scene use surface collisions?

(18-03-2022, 02:46 PM)josemendez Wrote: In case you're not using surface collisions at all, then the behavior you describe doesn't make sense. Would it be possible for you to share your project, or at least some scene that reproduces it?

Quote:if (contact.distance > 0.01) return;

Quote:if (particleIndex != hand.SolverIndex) return;

Quote:continue;

(21-03-2022, 11:34 AM)josemendez Wrote: Hi!

Just realized that your code to iterate over all contacts does this:


Which means that once you find the first speculative contact, you exit the function and simply ignore any other contacts.

Same for


If the first contact in the list is not the one you're looking for, you just stop looking. So your interaction code might or might not work based purely on whether the hand contact is the first one to appear on the list, which is of course 100% luck based .

replace these "return;" with


The continue keyword simply jumps to the next iteration of a loop, ignoring all instructions that appear after it in the current iteration. That way, you skip speculative contacts and contacts that you're not interested in, but still process all other contacts to look for the one you want. Still haven't tried the project you sent me but this bug quite likely plays a huge role on the weird behavior you get. Will download the project and try it nonetheless.

Edit: tried the project, and this bug was the culprit indeed. Fixed code:

Code:

// Just iterate over all contacts in the current frame
foreach (Oni.Contact contact in handCollision.contacts)
{
                // This one is an actual collision
                if (contact.distance > 0.01)
                    continue;

                // Get the particle index directly, as all simplices are guaranteed to have size 1:
                int particleIndex = hand.Solver.simplices[contact.bodyA];

                // This is not the particle you are looking for - Obi Wan
                if (particleIndex != hand.SolverIndex) continue;

                // Retrieve collider
                ObiColliderBase collider = ObiColliderWorld.GetInstance().colliderHandles[contact.bodyB].owner;

                // Attach hand and collider
                hand.Grab(collider.transform);
}