unity how can I convert transform.position into physical movement?

Question

In my code I move the player with transform.position but this creates problems with colliders and the physic of my game.

 transform.position = new Vector3(
                transform.position.x + touch.deltaPosition.x * multiplier,
                transform.position.y,
                transform.position.z + touch.deltaPosition.y * multiplier)

How can I convert this to velocity or some physical movement so that the speed get not effect?

Answer 1

In general as soon as there is a Rigidbody and collisions involved you should avoid two things:

• Moving your object via the transform
• Moving your object in Update

Both breaks the physics.

What you rather want to do is either directly update the Rigidbody.velocity. It is fine to do that in Update

// If possible already reference via Inspector
[SerializeField] private Rigidbody _rigidbody;

private void Start()
{
    if(!_rigidbody) _rigidbody = GetComponent<Rigidbody>();
}

private void Update()
{
    ...

    _rigidbody.velocity = Vector3.right * touch.deltaPosition.x * multiplier 
        + Vector3.forward * touch.deltaPosition.y * multiplier;
    ...
}

The alternative is to separate the User input (Update) from the physics routine (FixedUpdate) and use MovePosition

(assuming your code is executed in Update)

private Vector3 targetPosition;

// If possible already reference via Inspector
[SerializeField] private Rigidbody _rigidbody;

private void Start()
{
    if(!_rigidbody) _rigidbody = GetComponent<Rigidbody>();

    targetPosition = transform.position;
}

private void Update()
{
    ...

    targetPosition = _rigidbody.position 
        + Vector3.right * touch.deltaPosition.x * multiplier 
        + Vector3.forward * touch.deltaPosition.y * multiplier;

    ...
}

private void Update()
{
    _rigidbody.MovePosition(targetPosition);
}