ForcePull.cs (for VRTK v3)

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ForcePull : MonoBehaviour {
    public float grabRadius = .25f;
    public float grabForce = 5;
    public float grabRange = 100;
    public float emitRate = 16;
    // VRTK.VRTK_ControllerEvents cEv;
    VRTK.VRTK_InteractGrab grabber;
    VRTK.VRTK_InteractUse user;
    void Start () {
        // cEv = GetComponent<VRTK.VRTK_ControllerEvents> ();
        grabber = GetComponent<VRTK.VRTK_InteractGrab> ();
        if (grabber == null) { grabber = gameObject.AddComponent<VRTK.VRTK_InteractGrab> (); }
        user = GetComponent<VRTK.VRTK_InteractUse> ();
        if (user == null) { user = gameObject.AddComponent<VRTK.VRTK_InteractUse> (); }
        emitParams.startSize = 1;
        emitParams.startLifetime = 1;
        emitParams.startColor = telekenisisParticle.main.startColor.color;
    }

    GameObject line_ray, line_target, line_hit;
    public ParticleSystem telekenisisParticle;
    private ParticleSystem.EmitParams emitParams = new ParticleSystem.EmitParams();

    bool hadGravity;
    Rigidbody rbBeingMovedWithTheForce;

    Rigidbody GetRigidbodyFrom(GameObject go) {
        Rigidbody rb = go.GetComponent<Rigidbody> ();
        if (rb == null) {
            rb = go.GetComponentInParent<Rigidbody> ();
        }
        return rb;
    }

    float timer;
    // Update is called once per frame
    void Update () {
        timer -= Time.deltaTime;
        Rigidbody rbBeingPointedAt = null;
        Vector3 raydir = -transform.right;
        if (user.IsUseButtonPressed() && !grabber.IsGrabButtonPressed ()) {
            Vector3 camDir = transform.forward;
            if (Camera.main != null) {
                camDir = Camera.main.transform.forward;
            }
            float alignment = Vector3.Dot (raydir, camDir);
    //      NS.Lines.MakeArrow (ref line_ray, transform.position, transform.position + raydir, Color.gray);
            if (alignment > .5f) {
                RaycastHit rh = new RaycastHit ();
                Vector3 rayStart = transform.position - raydir * grabRadius;
                // get all the objects in range
                RaycastHit[] hits = Physics.SphereCastAll (rayStart, grabRadius, raydir, grabRange);
//              if (Physics.SphereCast (rayStart, grabRadius, raydir, out rh)) {
                Vector3 emitFrom = rayStart + raydir * grabRange;;
                if(hits != null) {
    //          NS.Lines.MakeCircle (ref line_hit, rh.point, rh.normal, Color.black, grabRadius);
    //          telekenisisParticle.transform.position = rh.point;
                    // select the one that is the most well aligned, and closest
                    int bestIndex = -1;
                    float bestScore = float.PositiveInfinity;
                    for (int i = 0; i < hits.Length; ++i) {
                        Rigidbody rb = GetRigidbodyFrom (hits [i].collider.gameObject);
                        if (rb != null) {
                            Vector3 delta = hits [i].point - rayStart;
                            float dist = delta.magnitude;
                            float align = (1 - Vector3.Dot (raydir, delta / dist));
                            float score = dist * align * align;
                            if(bestIndex < 0 || score < bestScore){
                                bestScore = score;
                                bestIndex = i;
                                rbBeingPointedAt = rb;
                                emitFrom = hits [i].point;
                            }
                        }
                    }
                    // if none are selected, show where the hand is pointing
                    if (timer < 0) {
                        if (rbBeingPointedAt == null) {
                            if (Physics.Raycast (rayStart, raydir, out rh, grabRange)) {
                                emitFrom = rh.point;
                            }
                        }
                        if(telekenisisParticle != null) {
                            //telekenisisParticle.Emit (emitFrom, -raydir * 1, 1, 1, telekenisisParticle.main.startColor.color);
                            emitParams.position = rh.point;
                            emitParams.velocity = -raydir;
                            telekenisisParticle.Emit(emitParams, 1);
                        }
                    }
                }
            }
        }
        if (rbBeingPointedAt != rbBeingMovedWithTheForce) {
            if (rbBeingMovedWithTheForce != null) {
                if (hadGravity) {
                    rbBeingMovedWithTheForce.useGravity = true;
                }
                rbBeingMovedWithTheForce = null;
            }
            if (rbBeingPointedAt == null) {
                //Debug.Log ("Stopped acting on " + rbBeingMovedWithTheForce);
            }
            rbBeingMovedWithTheForce = rbBeingPointedAt;
            if (rbBeingMovedWithTheForce != null) {
                hadGravity = rbBeingMovedWithTheForce.useGravity;
                rbBeingMovedWithTheForce.useGravity = false;
                //Debug.Log ("Acting on " + rbBeingMovedWithTheForce);
            }
        }
        float speed = 1;
        if (rbBeingMovedWithTheForce != null) {
            //NS.Lines.MakeArrow (ref line_ray, transform.position, acting.transform.position, Color.gray);
            //NS.Lines.MakeCircle(ref line_target, acting.transform.position, raydir, Color.gray, grabRadius);
            //telekenisisParticle.transform.position = rbBeingMovedWithTheForce.transform.position;
            Vector3 delta = transform.position - rbBeingMovedWithTheForce.position;
            float dist = delta.magnitude;
            //Vector3 dir = delta / dist;
            if (dist > 1) {
                speed = dist;
            }
            Vector3 idealV = -raydir * speed;
            Vector3 accel = idealV - rbBeingMovedWithTheForce.velocity;
            rbBeingMovedWithTheForce.velocity += accel.normalized * grabForce * Time.deltaTime;
            if (timer < 0) {
                // telekenisisParticle.Emit (transform.position, raydir * speed, 1, 1, telekenisisParticle.main.startColor.color);
                emitParams.position = transform.position;
                emitParams.velocity = raydir * speed;
                telekenisisParticle.Emit(emitParams, 1);
            }
        }
        if (timer < 0) {
            timer = 1/emitRate;
        }
    }
}