[Solved] Rotation of an arrow that shows the direction of the force

Hello everyone,

I'm having some troubles understanding rotations in Unity v2018.

I'm trying to locate an arrow that points out the direction of the force that an sphere feels according to the origin (0,0,0).

The way I'm calculating the force vector is as follows

Code (CSharp):

1. float distance = position.magnitude;
2. Vector3 force = (distance > 0.5) ? (q1 * q2 / (distance * distance)) * position.normalized : Vector3.zero;

Q1 and Q2 are the values of the spheres and position is the position of Q2 (the one that I can control).

The way I'm relocating the arrow is as follows:

Code (CSharp):

1.            float angleArrow = Mathf.Acos(Vector3.Dot(new Vector3(0, 1, 0), force) / force.magnitude);
2. Vector3 axisArrowRot = Vector3.Cross(new Vector3(0, 1, 0), force);
3. arrow.transform.rotation = Quaternion.identity * Quaternion.LookRotation(axisArrowRot * angleArrow);

Currently what I get is the following behaviour:

The thing is that i want the arrow follow the direction of the orange line.

I hope you could help me understand what my problem is.

 

There are some strange things in your code for sure, like multiplying by Quaternion.identity (which does nothing), or multiplying axisArrowRot by a float before passing it to LookRotation (which would also do nothing — what matters is the direction, not the magnitude).

I think all you should have to do for this is something like

Code (csharp):

1. arrow.transform.rotation = Quaternion.LookRotation(Q2pos - Q1pos);

where Q1pos and Q2pos are the positions of the two spheres.

 

It still does not behavior as expected . I erased the Quaternion.identity, thanks for pointing it out

 

The answer is always localRotation instead of rotation
*edit: usually*

 

I tried to change it into

Code (CSharp):

1. arrow.transform.localRotation= Quaternion.LookRotation(axisArrowRot * angleArrow);

but same behavior

 

I created a base case with the behavior explained at the beginning of the thread. I hope it helps the community and you guys to understand my problem

 

Solved, I just changed the following lines in the code of AvatarScript uploaded

Code (CSharp):

1. arrow.transform.position = transform.position;
2.            
3.             float angleArrow = Mathf.Acos(Vector3.Dot(new Vector3(0, 1, 0), force) / force.magnitude);
4.             Vector3 axisArrowRot = Vector3.Cross(new Vector3(0, 1, 0), force);
5.             arrow.transform.rotation = Quaternion.identity * Quaternion.LookRotation(force, axisArrowRot * angleArrow);

And got the desired behavior