Rotate object without storing facing

Question

Hello, I'm rather new at using Unity, so I apologize if t$$anonymous$$s is trivial, but I haven't found a good solution for it online.

I've made a cube out of 6 planes, grouped them and added them to an empty game object with the location of the center of the cube and added my rotate script to it.

I want to move and rotate t$$anonymous$$s cube 90 degrees in one of four direction when pressing a key (just press, not holding down). I've got the translation working great, however the rotation is giving me trouble. I've tried :

   Quaternion toRotation = transform.rotation;
    toRotation *= Quaternion.Euler(rotationToadd);

And then Quaternion.Slerp() and it works well when moving only left to right or front to back, but when I move forward and then left the rotation is messed up.

What I would like to do is add or substract 90 degrees from the cube's rotation, no matter w$$anonymous$$ch way it's facing. E.g. add 90 degrees on Z axis => cube rotates =>new rotation is still (0,0,0).

Answer 1

Best Answer

Answer by Scribe · May 23, 2018 at 05:05 PM

Rather than using Quaternion.Euler try Quaternion.AngleAxis in t$$anonymous$$s case the angle will always be +/-90 and you choose the axis to rotate around. To rotate horizontally that would be Vector3.up for vertical it would be Vector3.right.

Edit So I forgot an important bit! What makes the AngleAxis method a useful one is that we can transform the axis into local space w$$anonymous$$ch isn't so easily done using a Eulerian representation. In the context of your code t$$anonymous$$s looks like:

     Vector3 axis = ...;
     Quaternion fromRotation = transform.rotation;
     Vector3 localAxis = transform.InverseTransformDirection(axis);
     Quaternion toRotation = transform.rotation * Quaternion.AngleAxis(rotationToadd, localAxis);

Hope that helps!

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lazyfuntimesolutions · May 25, 2018 at 01:19 PM 0

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Thanks for your answer, that's definitely the method I need. However I'm unsure how to use it properly. This is what I have so far and the problem is still there. Quaternion fromRotation = transform.rotation; Quaternion toRotation = transform.rotation * Quaternion.AngleAxis(rotationToadd, axis);

         float elapsed = 0.0f;
         while (elapsed < duration)
         {
             transform.rotation = Quaternion.Slerp(fromRotation, toRotation, elapsed / duration);
             elapsed += Time.deltaTime;
             yield return null;
         }
         transform.rotation = toRotation;

Scribe lazyfuntimesolutions · May 25, 2018 at 04:47 PM 1

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Can you add the code you are using to find 'axis' please :)

lazyfuntimesolutions Scribe · May 26, 2018 at 03:57 PM 0

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Of course, thank you for taking an interest :) Here's all I've got:

   void FixedUpdate()
     {
         if (Input.anyKeyDown && !moving && !rotating)
         {
             Vector3 movementVector = Vector3.zero;
 
             if (Input.GetKeyDown(KeyCode.D))
             {
                 movementVector = new Vector3(1, 0, 0);
                 StartCoroutine(Rotate(-90, Vector3.forward, .2f));
             }
             else
             if (Input.GetKeyDown(KeyCode.A))
             {
                 movementVector = new Vector3(-1, 0, 0);
                 StartCoroutine(Rotate(90, Vector3.forward, .2f));
             }
             else
             if (Input.GetKeyDown(KeyCode.W))
             {
                 movementVector = new Vector3(0, 0, 1);
                 StartCoroutine(Rotate(90, Vector3.right, .2f));
             }
             else
             if (Input.GetKeyDown(KeyCode.S))
             {
                 movementVector = new Vector3(0, 0, -1);
                 StartCoroutine(Rotate(-90, Vector3.right, .2f));
             }
 
             if (!movementVector.Equals(Vector3.zero))
             {
                 startPosition = transform.position;
                 endPosition = startPosition + movementVector;
                 journeyLength = Vector3.Distance(startPosition, endPosition);
 
                 startTime = Time.time;
                 moving = true;
                 rotating = true;
 
             }
         }
 
         if (moving)
         {
             float distCovered = (Time.time - startTime) * moveSpeed;
             float fracJourney = distCovered / journeyLength;
 
             transform.position = Vector3.Lerp(startPosition, endPosition, fracJourney);
             if (transform.position.Equals(endPosition))
             {
                 moving = false;
             }
         }
     }
 
     IEnumerator Rotate(float rotationToadd, Vector3 axis, float duration)
     {
         Quaternion fromRotation = transform.rotation;
         Quaternion toRotation = transform.rotation * Quaternion.AngleAxis(rotationToadd, axis);
 
         float elapsed = 0.0f;
         while (elapsed < duration)
         {
             transform.rotation = Quaternion.Slerp(fromRotation, toRotation, elapsed / duration);
             elapsed += Time.deltaTime;
             yield return null;
         }
         transform.rotation = toRotation;
         rotating = false;
     }

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Rotate object without storing facing

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