Rigidbody.MoveRotation - How to count backflips/frontflips ?

Question

Hi guys, I want my game to display the number of flips the character does, how can I implement that ?

     void FixedUpdate () 
     {
         float rotate = Input.GetAxis ("Vertical");
         rigidbody2D.MoveRotation(rigidbody2D.rotation + 20 * Time.deltaTime * rotate * 100);
     }

Answer 1

Best Answer

Answer by DGKN · Jul 12, 2014 at 05:06 PM

Seems like I've found a solution :

     float flips = 0;
     float deltaRotation = 0;
     float currentRotation = 0;
     float WindupRotation = 0;
 
 deltaRotation = (currentRotation - transform.eulerAngles.z);
         currentRotation = transform.eulerAngles.z;
         if (deltaRotation >= 300) 
             deltaRotation -= 360;
         if (deltaRotation <= -300) 
             deltaRotation += 360;
         WindupRotation += (deltaRotation);
 
         flips = WindupRotation / 360;

This shows me how many degrees my character rotates even if it's more than 360°. Then I just have to divide it by 360 to know how many flips it has done.

Example : Player rotates -720° -> -720/360 = -2 (Which means 2 backflips) Player rotates +720° -> 720/360 = 2 (Which means 2 frontflips)

It seems to work right now, but do you guys think this is the proper way to count flips ?

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Answer 2

Answer by dsada · Jul 12, 2014 at 02:09 PM

You can check the transform.eulerangles value in the LateUpdate() function. Lets say your character did a flip if it reaches the 350-360 interval. Then you increment your flip value and set a boolean variable to dont increment until it does not leave this interval. After its left you can check again.

This is the first idea that came into my mind maybe there are more elegant ways to check but its not trivial because of the repeation of the 0-360 values.

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DGKN · Jul 12, 2014 at 02:31 PM 0

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Thanks, but how do I check if it has reached the 350-360 interval though ? Is this the proper way to check it ?

 if (transform.localEulerAngles.z > 350 && transform.localEulerAngles.z < 360)
             Debug.Log ("flip");

dsada · Jul 12, 2014 at 02:48 PM 0

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yes, thats good. However i've got really weird experiences with eulerangles. Sometimes its moving between -90 - 270 sometimes its 0 - 360. Observe your character and adjust the values to your needs.

DGKN · Jul 12, 2014 at 03:25 PM 0

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This is what I've found, but I can't code it, if anyone knows how to code this I'll be really happy.

"Basically, save the upright rotation into one variable at the start, for example "Quaternion normalRotation". Then, create a new variable that is a Quaternion that is 359 degrees different from normalRotation on the same axis. Whenever your player reaches this newRotation, you can count it as a back/front flip. This is pseudo-pseudo code, but I hope this helps. "

Answer 3

Answer by robertbu · Jul 12, 2014 at 03:40 PM

In many situations, eulerAngles does not give back what you want. There are multiple eulerAngle representations for any rotation, and sometimes Unity changes the representation. For 2D, you can use ATan2(). Assuming you are rotating counterclockwise, you can do something like this:

 Vector3 dir = transform.right;
 float angle = Mathf.Atan2(dir.y, dir.x) * Mathf.Rad2Deg;
 if ((prevAngle > -10.0f && prevAngle < 0.0f) && angle >= 0.0) {
      flips++
 }
 prevAngle = angle;

Note that Mathf.Atan2() returns angles in -180 to 180. The sign will flip when it goes form -180 to 180, so you cannot just check the sign. That is way the 'prevAngle > -10.0f' is included. 'prevAngle' is a class instance variable. Atan2 returns 0.0 for Vector3.right. So when the 'transform.right' is equal to 'Vector3.right' the angle will be 0.0.

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DGKN · Jul 12, 2014 at 04:13 PM 0

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Thanks robert, I'm playing with your code to make it work because right now, when I rotate a few degrees left (eg: -20°), it increments flips and then it seems to work but when I rotate at high speed, it doesn't seem to save flip counts anymore

Should I use it in Update or FixedUpdate ? Right now, I'm using Update

Rigidbody.MoveRotation - How to count backflips/frontflips ?

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