Help Grab Rope - VR

[josemendez]

Another astute suggestion, thanks. However I made that change, then moved the line to Start() to avoid the issue of the rope not being initialised yet, and now there's no collisions registering at all, which has frankly confused me even more than it would have if there was no effect.   

You're getting a reference to the solver in Start(), which is called after OnEnable() (see: https://docs.unity3d.com/Manual/ExecutionOrder.html). However you're subscribing to the solver collisions in OnEnable(), so solver == null at that point.

You should get the solver in OnEnable(), then subscribe to its collision event:

Code:

private void OnEnable()
    {
        solver = rope.solver;
        if (solver != null)
            solver.OnCollision += Solver_OnCollision;
    }

Another issue is that you're converting the contact particle index (which is already a solver index, since contacts are reported per-solver, not per-actor) to a solver index again. This line:

Code:

int solverIndex = rope.solverIndices[contact.particle];

should just be

Code:

int solverIndex = contact.particle;

The problem with indexing the actor's solverIndices array this way is that you risk out of bounds accesses (runtime error) at worst or non-functional attachments at best. The same issue exists when passing the particle index to the pin constraint, so replace the AddConstraint line with this:

Code:

batch.AddConstraint(solverIndex, obiCollider, positionCS, Quaternion.identity, 0, 0, float.PositiveInfinity);

That gets everything working properly for me. cheers!