Quaternion rotate point around pivot?

Hi all,

Newbie here. I've seen similar questions asked but without a clear enough answer for me. I'm trying to rotate a Vector3 point by x degrees based on another Vector3 point acting as the pivot. For now I'm just looking for a rotation around Y axis and distance between the point and pivot never changes.

Closest I've got is something like:
Vector3 point = new Vector3 (0, 0, 0);
Vector3 pivot = new Vector3(2,0,2);
float angle = 30;
Quaternion rotate = Quaternion.AngleAxis(angle, Vector3.up) ;
Vector3 new_point = rotate * point;

However Quaternion.AngleAxis seems to only rotate around the World Y Axis, how can I do the equivalent with the pivot vector acting as the placement for the Y axis? I can achieve this in the editor with GameObjects but want to be able to translate straight vector points in space if possible.

This may just need to be some manual C# code to calculate this but I suspect Unity have supplied a way to do this with Quaternions and I just can't work it out.

Kind regards and thanks for any help!
David

 

You can use transform.RotateAround(). I set up a scene with a cube as my target. Here is some code that makes the camera (or other attached object) rotate around the cube:

Code (CSharp):

1. public Transform target;
2.     public float speed = 10;
3.  
4.     void Update() {
5.         transform.RotateAround(target.position, target.up, speed * Time.deltaTime);
6.     }

This rotates around the cube's up vector.

 

Hi, thanks for the quick reply!

I'm looking to rotate Vector3 points which as far as I'm aware don't have any transform properties.

I might be looking at the problem wrong but currently am looking to manipulate a list of vectors that make up a path that gets used later, not at the time of the rotate.

Cheers
David

 

Ah, I see. I think you just have to do the math then. It looks like someone has already done the math so I'll just link it instead of re-doing it. http://answers.unity3d.com/questions/532297/rotate-a-vector-around-a-certain-point.html

 

Thanks. I've actually tried that code - I've got it working now, but it wasn't earlier - think I had misaligned loops from capturing the rotation to applying to my list. Still good to see even though a tiny bit of math in there the Quaternion.Euler is still useful. Multiplying a quaternion with a vector is interesting to say the least!

 

What if you want rotate by X and Y ....Invoke this this function two times?