Help Rope extension, vibration and collision

[josemendez]

 
How can I find the colliding particle from this code? That is, how can I detect (particle/all particle)?
Is the simplexStart value here my index that is experiencing the collision?

No, "particleIndex" is as the comment in the code points out. "simplexStart" is the first entry in the simplices array, and "simplexSize" the size of the simplex. So when a simplex collides, you get a start and a size. The indices of the colliding particles are stored in solver.simplices[simplexStart] to solver.simplices[simplexStart+simplexSize].

Surface-based uncheck

If none of your ropes use surface-based collisions, all simplices in the solver have size 1 and it's not needed to iterate over all particles in each simplex. You can just do what you were doing before:

Code:

int particleIndex = solver.simplices[contact.bodyA];

I just tried the script and it works perfectly for me. I'm attaching the version of the script that I used to perform the test, maybe you can spot any difference with what you're doing?

Code:

using UnityEngine;
using Obi;

public class RopeContactNormalized : MonoBehaviour
{
    public ObiRope rope;

    // Start is called before the first frame update
    void Start()
    {
        rope.solver.OnCollision += OnRopeContactEnter;
    }

    public void OnRopeContactEnter(ObiSolver solver, ObiNativeContactList contacts)
    {
        var world = ObiColliderWorld.GetInstance();
        float normalizedCoordinate = -1;

        foreach (var contact in contacts)
        {
            if (contact.distance > 0.001f) continue;

            int particleIndex = solver.simplices[contact.bodyA];
            var col = world.colliderHandles[contact.bodyB].owner;

            if (rope != null)
            {
                var elements = rope.elements;

                int elementIndex = -1;

                for (int i = 0; i < elements.Count; ++i)
                {
                    var element = elements[i];
                    if (element.particle1 == particleIndex || element.particle2 == particleIndex)
                    {
                        elementIndex = i;
                        break;
                    }
                }

                if (elementIndex != -1)
                {
                    normalizedCoordinate = (float)elementIndex / elements.Count;
                    Debug.Log("Normalized rope position: " + normalizedCoordinate);
                    break;

                }
                else
                {
                    Debug.LogWarning("Element not found for particle " + particleIndex);
                }
            }
            else
            {
                Debug.LogWarning("Rope reference is missing!");
            }
        }

        if (normalizedCoordinate >= 0)
        {
            var section = rope.GetComponent<ObiPathSmoother>().GetSectionAt(normalizedCoordinate);
            Debug.DrawRay(section.position, section.normal, Color.red);
        }
    }
}