Setting Rigidbody.velocity at each frame makes the character jittery

Hello!

I work on a 3D game in which the main chracter is seen from above and is controlled with the mouse cursor. When clicked on the terrain the character will rotate and start moving towards the pointed location. The trick is that he will be moving while rotating, so I have to update the velocity for the rigidbody at each frame while rotating.

Code (CSharp):

1.     public IEnumerator MoveTo(Vector3 destination)
2.     {
3.         while (true) {
4.            //update the velocity
5.            _rgb.velocity = _myTransform.forward * movementSpeed;
6.            
7.             Vector3 targetPoint = destination - _myTransform.position;
8.             Quaternion targetRotation = Quaternion.LookRotation (targetPoint, Vector3.up);
9.             _myTransform.rotation = Quaternion.Slerp (_myTransform.rotation, targetRotation, Time.deltaTime * turnSpeed);
10.  
11.             Vector3 forward = _myTransform.TransformDirection (Vector3.forward);
12.             Vector3 toOther = destination - _myTransform.position;
13.              
14.             // check if character finished rotating
15.             if (Vector3.Dot (forward.normalized, toOther.normalized) > .99f )
16.                 break;
17.             // check if character reached destination while rotating
18.             if( Mathf.Abs(_myTransform.position.x - destination.x) < .5f)
19.             {
20.                 if( Mathf.Abs(_myTransform.position.z - destination.z) < .5f)
21.                 {
22.                     StopMoving();
23.                     return false;
24.                 }
25.             }
26.             yield return null;
27.         }
28.         while( (Vector2.Distance(new Vector2(_myTransform.position.x - _myTransform.forward.x *.5f, _myTransform.position.z - _myTransform.forward.z *.5f),
29.                                         new Vector2(destination.x, destination.z))) > .5f)
30.         {
31.  
32.             yield return null;
33.         }
34.  
35.         StopMoving();
36.     }

The problem is this makes the character jittery while rotating (the first "while"). After he finishes rotating he will smoothly translate to the desired location.

Anyone knows what is the cause here? I assumed that is because I change the velocity at each frame, which (if it works the way I think it works) shouldn`t be the cause, but there is no other line of code in there that could affect it.

 

Try making the change every FixedUpdate instead of every Update:

yield return new WaitForFixedUpdate();

Instead of:

yield return null;

 

I tried and no change. I used WaitForEndOfFrame() too and is still the same.

I tested without the velocity update and it`s still jittery. So it means my assumption was wrong. The problem should be the way I assigned the rotation I think.

 

better idea. dont use a co-routine.

 

Got rid of coroutines and made a state machine like structure:

Code (CSharp):

1. void FixedUpdate () {
2.         switch (state) {
3.         case State.Idle:
4.             break;
5.         case State.Moving: MoveTowardsDestinaion();
6.             break;
7.         case State.Rotating: RotateTowardsDestination();
8.             break;
9.         }
10.     }

It works now, thanks for your suggestion.

 

Also, a rigidbody should be moved and rotated using Rigidbody.MovePosition and Rigidbody.MoveRotation instead of just modifying the transform. This ensures the rb interacts correctly with the other physic objects.