Rotate object in 45 degree steps

Question

Hello! I have a 2D character which only has graphics for 45° rotations. That means: top, topright, right, downright, down, etc ..

I want to character rotate to the cursor. I have the vector from the character's position to the cursor's position in the world. Only x and z matters to me here. How do i find out the closest possible direction (top, topright,..) from that vector?

The code for this so far:

 var hit : RaycastHit;
         var ray : Ray = camera.main.ScreenPointToRay (Input.mousePosition);
         if (Physics.Raycast (ray, hit)) {
             Debug.DrawLine (transform.position, hit.point);
             cursorWorldPos = hit.point;
             cursorWorldPos.y = transform.position.y;
             aimingDirection = cursorWorldPos - transform.position;

Answer 1

One solution is to use Mathf.Atan2():

 #pragma strict 
  
 function Update() {
     var hit : RaycastHit;
     var ray : Ray = camera.main.ScreenPointToRay (Input.mousePosition);
     if (Physics.Raycast (ray, hit)) {
         Debug.DrawLine (transform.position, hit.point);
         var cursorWorldPos = hit.point;
         var aimingDirection = cursorWorldPos - transform.position;
         var angle = -Mathf.Atan2(aimingDirection.z, aimingDirection.x) * Mathf.Rad2Deg + 90.0;
         angle = Mathf.Round(angle / 45.0f) * 45.0f;
         transform.rotation = Quaternion.AngleAxis(angle, Vector3.up);
     }
 }

Note if the camera is looking straight down, then you don't need the raycast. You can use ScreenToWorldPoint():

 #pragma strict 
  
 function Update() {
     var pos = Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.transform.position.y - transform.position.y);
     pos = camera.main.ScreenToWorldPoint(pos);
     var aimingDirection = pos - transform.position;
     var angle = -Mathf.Atan2(aimingDirection.z, aimingDirection.x) * Mathf.Rad2Deg + 90.0;
     angle = Mathf.Round(angle / 45.0f) * 45.0f;
     transform.rotation = Quaternion.AngleAxis(angle, Vector3.up);
 }

If the camera is at an angle, then it would be somewhat more efficient to do a Collider.Raycast(). It would be even more efficient to do a Plane.Raycast().

Rotate object in 45 degree steps

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