Adapt force Vector3 to directional Vector3

Question

I have a Vector3 that indicates the input force of the player to the ball

Vector3(moveHorizontally, 0.0f, moveVertically);

I have another Vector3 that indicates the normalized direction of a plane

Vector3(-1.0f, 0.0f, 0.0f);

How can I make the ball follow the direction of the object using AddForce()? In this case, I think the ball should go left instead of front if I'm not mistaking.

EDIT: I need no move a ball forward in a certain direction. Each time the ball triggers a plane, the direction of the plane is facing becomes the direction of the ball. It's a game where the ball rolls on a non-linear track with turns.

You will have to explain and show more of your environment. Can you make a minimal reproducible example of the part which implements the ball movement and the plance? Then we could propose how to implement the desired effect. — Yunnosch
Simply trigger it with a collider, read plane direction and pass the direction as a parameter into AddForce. — Dave

derHugo derHugo · Accepted Answer · 2019-01-25T17:59:10

I would not use AddForce since I guess you want to change the direction immediately when colliding.

I think what you mean is something like

private rigidBody;

private void Awake()
{
    rigidBody = GetComponent<RigidBody>();
}

private void OnCollisionEnter(Collision col)
{
    // Or however you want to check with what you are colliding
    if(col.gameObject.tag != "Plane") return;

    var hitPlane = col.gameObject;
    var invertedPlaneNormal = hitPlane.transform.forward.normalized * -1;

    var currentSpeed = rigidBody.velocity.magnitude;

    // Keep same velocity but change direction immediately
    rigidBody.velocity = invertedPlaneNormal * currentSpeed;
}

you could also add damping like

[Range(0,1)]
public float dampFactor;

//...

rigidBody.velocity = invertedPlaneNormal * currentSpeed * (1 - dampFactor);

Adapt force Vector3 to directional Vector3

2 Answers