Rotate an object smoothly by 90 degrees on key press in unity3D

Question

[I saw few similar question on stackexchange but none is solving the purpose.]

I want to rotate a 3D object by 90 degrees on different axis on respective inputs. For example if 'a' is pressed, the object should rotate left by 90 degrees. transform.Rotate(0,90,0); is working but it is not rotating the object smoothly.

I am new to C# and js so cannot manually code but I tried the codes given in this answer at Rotate an object smoothly on the Y axis in Unity. The below code works but it it has two problems - code:

void Update () {
SwingOpen();
}

void SwingOpen()
{   
    Quaternion newRotation = Quaternion.AngleAxis(90, Vector3.up);
    transform.rotation= Quaternion.Slerp(transform.rotation, newRotation, .05f);      
}

Problem 1: The above code rotates object without any keyboard inputs. I added the condition if (Input.GetKeyDown (KeyCode.RightArrow)) but now the object rotates partially on every keyboard input. I want to rotate it by 90 degrees on a single key press.

Problem 2: It will never actually rotate the object by 90 deg. It will always be tending towards 90 deg. I want exact 90 deg rotation to allow multiple 90 deg rotations for 'n' number if inputs.

How can I solve this? Please help. Please let me know if the question isn't clear enough.

[EDIT]

I applied the below script but it is giving me some totally unexpected output

Code:

public float speed = 1;
private int xtimesHit = 0;
private int ytimesHit = 0;
private int ztimesHit = 0;

void Update () {
    if( Input.GetKeyDown( KeyCode.RightArrow ) ){
        ztimesHit--;
    }
    if( Input.GetKeyDown( KeyCode.LeftArrow ) ){
        ztimesHit++;
    }


    if( Input.GetKeyDown( "a" ) ){
        ytimesHit++;
    }
    if( Input.GetKeyDown( "d" ) ){
        ytimesHit--;
    }


    if( Input.GetKeyDown( "w" ) ){
        xtimesHit++;
    }
    if( Input.GetKeyDown( "s") ){
        xtimesHit--;
    }

    this.transform.rotation = Quaternion.Lerp(this.transform.rotation, Quaternion.Euler(xtimesHit*90,ytimesHit*90,ztimesHit*90), Time.deltaTime*speed);

}

On running this script If I press rightarrow once followed by 's' the object rotates on 'z' axis and 'x' axis correctly but there after if I press arrowkeys or 'a/s' in both the cases the object rotates on y axis. I dont understand why this is happening.

I want it to rotate w.r.t. the world axis always.

Answer 1

This is how I would do it

private Quaternion startingRotation;
public float speed = 10;

void Start(){
    //save the starting rotation
    startingRotation = this.transform.rotation;
}

void Update () {
    //return back to the starting rotation
    if( Input.GetKeyUp( KeyCode.RightArrow ) || Input.GetKeyUp( KeyCode.LeftArrow ) ){
        StopAllCoroutines();
        StartCoroutine(Rotate(0));
    }

    //go to 90 degrees with right arrow
    if( Input.GetKeyDown( KeyCode.RightArrow ) ){
        StopAllCoroutines();
        StartCoroutine(Rotate(90));
    }

    //go to -90 degrees with left arrow
    if( Input.GetKeyDown( KeyCode.LeftArrow ) ){
        StopAllCoroutines();
        StartCoroutine(Rotate(-90));
    }

}

IEnumerator Rotate(float rotationAmount){
    Quaternion finalRotation = Quaternion.Euler( 0, rotationAmount, 0 ) * startingRotation;

    while(this.transform.rotation != finalRotation){
        this.transform.rotation = Quaternion.Lerp(this.transform.rotation, finalRotation, Time.deltaTime*speed);
        yield return 0;
    }
}

---

Edit # 1

public float speed = 1;
private int timesHit = 0;

void Update () {
    if( Input.GetKeyDown( KeyCode.RightArrow ) ){
        timesHit++;
    }
    if( Input.GetKeyDown( KeyCode.LeftArrow ) ){
        timesHit--;
    }

    this.transform.rotation = Quaternion.Lerp(this.transform.rotation, Quaternion.Euler(0,timesHit*90,0), Time.deltaTime*speed);

}

---

Edit #2

Perhaps like this?

public float speed = 1;
private GameObject endRotation;

void Start(){
    endRotation = new GameObject();
}

void Update () {
    if( Input.GetKeyDown( KeyCode.RightArrow ) ){
        endRotation.transform.Rotate(Vector3.forward, 90, Space.World);
    }
    if( Input.GetKeyDown( KeyCode.LeftArrow ) ){
        endRotation.transform.Rotate(Vector3.forward, -90, Space.World);
    }


    if( Input.GetKeyDown( "a" ) ){
        endRotation.transform.Rotate(Vector3.up, 90, Space.World);
    }
    if( Input.GetKeyDown( "d" ) ){
        endRotation.transform.Rotate(Vector3.up, -90, Space.World);
    }


    if( Input.GetKeyDown( "w" ) ){
        endRotation.transform.Rotate(Vector3.left, 90, Space.World);
    }
    if( Input.GetKeyDown( "s") ){
        endRotation.transform.Rotate(Vector3.left, -90, Space.World);
    }

    this.transform.rotation = Quaternion.Lerp(this.transform.rotation, endRotation.transform.rotation, Time.deltaTime*speed);

}

Answer 2

Well, the solution here is pretty simple - if you don't know how to write your own code yet, you should definitely take a course rather than looking up code and trying to patch it in your program somehow without knowing at all how it works.

First, delcare a variable called currentFrame, and initially set it to -1. Also, make a variable called numOfFrames, and set it to the number of frames over which the change will occur.

void Update () {
    if(Input.GetKeyDown(KeyCode.RightArrow) && currentFrame == -1) {
        currentFrame = 0;
    }
    if(currentFrame >= 0 && currentFrame < numOfFrames) {
        SwingOpen();
        currentFrame = currentFrame + 1;
    }
}

void SwingOpen()
{   
    if (currentFrame == numOfFrames) {
        Quaternion newRotation = Quaternion.AngleAxis(90, Vector3.up);
        transform.rotation = newRotation;
        currentFrame = -1;
    }
    else {
        Quaternion newRotation = Quaternion.AngleAxis(90, Vector3.up);
        transform.rotation = Quaternion.Slerp(transform.rotation, newRotation, .05f);   
    }
}

Is this what you wanted? Obviously the code could probably be made cleaner but the concept will be the same.