DragRigidbody script, setting / unsetting to kinematic

Questions & Answers
1

Hello.

I’m using a default script from Unity called “DragRigidbody.cs”. My issue, or rather Question is: How can I set a Rigidbody to Kinematic by default, and then when I drag the object, have it change back to non-kinematic?

Just a note: I’m not a coder, and am from a design background. Please excuse my shoddiness, I’m still learning Unity and C#.

My first thought was to change the coroutine ‘DragObject’, and change it back to move the Rigidbody as normal. I’ve had a go at changing lines, and adding “.connectedBody.isKinematic = true” but I’ve had no luck. I’ve also tried splicing out and adding Kinematic here and there. Still no luck.

So I’ve come to the conclusion I’m doing something really wrong.

Specifically, the reason why I figured to set to the non-dragging objects to kinematic is because and when kinematic is set on, other rigidbodies don’t move on collision (unless I wanted to move them through other means outside of the drag script). I thought I’d also add an image to show what I mean.

alt text

So What I’m asking is: Is there a way that I can make the other objects kinematic while the one being dragged not kinematic. Either that, or another way, but I have no clue. Any help would be greatly appreciated.

The default Unity ‘DragRigidbody.cs’ script:

using System;
using System.Collections;
using UnityEngine;

namespace UnityStandardAssets.Utility
{
    public class DragRigidbody : MonoBehaviour
    {
        const float k_Spring = 50.0f;
        const float k_Damper = 5.0f;
        const float k_Drag = 10.0f;
        const float k_AngularDrag = 5.0f;
        const float k_Distance = 0.2f;
        const bool k_AttachToCenterOfMass = false;

        private SpringJoint m_SpringJoint;


        private void Update()
        {
            // Make sure the user pressed the mouse down
            if (!Input.GetMouseButtonDown(0))
            {
                return;
            }

            var mainCamera = FindCamera();

            // We need to actually hit an object
            RaycastHit hit = new RaycastHit();
            if (
                !Physics.Raycast(mainCamera.ScreenPointToRay(Input.mousePosition).origin,
                                 mainCamera.ScreenPointToRay(Input.mousePosition).direction, out hit, 100,
                                 Physics.DefaultRaycastLayers))
            {
                return;
            }
            // We need to hit a rigidbody that is not kinematic
            if (!hit.rigidbody || hit.rigidbody.isKinematic)
            {
                return;
            }

            if (!m_SpringJoint)
            {
                var go = new GameObject("Rigidbody dragger");
                Rigidbody body = go.AddComponent<Rigidbody>();
                m_SpringJoint = go.AddComponent<SpringJoint>();
                body.isKinematic = true;
            }

            m_SpringJoint.transform.position = hit.point;
            m_SpringJoint.anchor = Vector3.zero;

            m_SpringJoint.spring = k_Spring;
            m_SpringJoint.damper = k_Damper;
            m_SpringJoint.maxDistance = k_Distance;
            m_SpringJoint.connectedBody = hit.rigidbody;

            StartCoroutine("DragObject", hit.distance);
        }


        private IEnumerator DragObject(float distance)
        {
            var oldDrag = m_SpringJoint.connectedBody.drag;
            var oldAngularDrag = m_SpringJoint.connectedBody.angularDrag;
            m_SpringJoint.connectedBody.drag = k_Drag;
            m_SpringJoint.connectedBody.angularDrag = k_AngularDrag;
            var mainCamera = FindCamera();
            while (Input.GetMouseButton(0))
            {
                var ray = mainCamera.ScreenPointToRay(Input.mousePosition);
                m_SpringJoint.transform.position = ray.GetPoint(distance);
                yield return null;
            }
            if (m_SpringJoint.connectedBody)
            {
                m_SpringJoint.connectedBody.drag = oldDrag;
                m_SpringJoint.connectedBody.angularDrag = oldAngularDrag;
                m_SpringJoint.connectedBody = null;
            }
        }


        private Camera FindCamera()
        {
            if (GetComponent<Camera>())
            {
                return GetComponent<Camera>();
            }

            return Camera.main;
        }
    }
}
2

I’m not sure if this was the right way to go about it. But I seemed to have done what I wanted with a hacky solution.

First of all, rigidbodies are all set to Kinematic.

In the DragRigidBody script, at the end of Update before calling the Coroutine I added:

  m_SpringJoint.connectedBody.isKinematic = false;

Then moving down, adding this to the Coroutine:

    if (m_SpringJoint.connectedBody.isKinematic == true){
      m_SpringJoint.connectedBody.isKinematic = false;
    }

Finally, adding this to the ‘if(m_SpringJoint.connectedBody)’ statement:

    m_SpringJoint.connectedBody.isKinematic = true;

if there is a better way to go about doing this. Any advice for a beginner is welcomed.