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Counting an object's rotations?

Discussion in 'Scripting' started by bigkahuna, Mar 4, 2007.

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  1. bigkahuna

    bigkahuna

    Joined:
    Apr 30, 2006
    Posts:
    5,434
    I'm trying to come up with a bit of Javascript that counts the number of rotations for and object.

    I tried using "transform.Rotation" and "transform.EulerAngle", but Rotation resets itself when it reaches a second rotation and EulerAngle inverts when it passes 0 (zero).

    I thought about counting the number of times my object's rotation passes 0 (zero), but I'm afraid that if 0 is passed too quickly it won't be picked up by the script.

    Any other ideas or suggestions?
     
  2. jeffcraighead

    jeffcraighead

    Joined:
    Nov 15, 2006
    Posts:
    740
    You can count the # of inversions instead of 0s perhaps?
     
  3. StarManta

    StarManta

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    Oct 23, 2006
    Posts:
    8,777
    I'd suggest calculating the difference between the angle from frame to frame, and adding it together. That total / 360 = number of rotations.
     
  4. bigkahuna

    bigkahuna

    Joined:
    Apr 30, 2006
    Posts:
    5,434
    I probably didn't explain this well enough, but the object can rotate in either direction around it's Y axis. Imagine a "worm gear" and it can turn just so many times before reaching the end of the gear. So none of my original ideas would have worked. :?

    Thanks Craig - "Inversions"? I'm not sure what you mean, but I'll see what I can find.

    Thanks StarManta - I don't think that will work because the object can rotate in either direction.

    Thanks guys, keep the ideas coming!

    EDIT: Got it running, thanks!
     
  5. Omar Rojo

    Omar Rojo

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    Jan 4, 2007
    Posts:
    494
    Maybe this was posted before but it seems logical to me that if on a function you rotate an object by an angle X and if you have a variable T that adds X in the same function, T will always have the total rotation, for X positive and negative.

    Simple.

    Code (csharp):
    1.  
    2. var X = 0.0;
    3.  
    4. private var T = 0.0;
    5.  
    6. function Update ()
    7. {
    8.    transform.Rotate (0, X, 0);
    9.    T += X;
    10.  
    11.    Debug.Log ("Rotations: " + (T */ 360.0));
    12. }
    13.  
     
  6. bigkahuna

    bigkahuna

    Joined:
    Apr 30, 2006
    Posts:
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    Thanks Omar. I see what you're suggesting. Actually I'm using rotary forces to turn the worm gear and not directy rotating it, so I needed to track the object's rotation as a second function. (does that make sense?) If I understand what your code is doing, I don't think that's what I was looking for.

    The good news is that after spending an entire day on this, I finally got a piece of code together that worked. It ain't pretty, but so far it seems to work.

    Thanks again!
     
  7. Talzor

    Talzor

    Joined:
    May 30, 2006
    Posts:
    197
    He's probably rotating it in ways that doesn't give him any easy reference (e.g. with physics)

    @bigkahuna. Are you looking for something like this?
    Note that this has some limitations. It assumes that the object is only rotating in Y and that the rotation is no more than 180 degress in either direction pr. frame.

    Code (csharp):
    1.  
    2. using UnityEngine;
    3. using System.Collections;
    4.  
    5. public class CountRotations : MonoBehaviour {
    6.     private float totalRotation = 0;
    7.     public int nrOfRotations {
    8.         get {
    9.             return ((int) totalRotation)/360;  
    10.         }  
    11.     }
    12.    
    13.     private Vector3 lastPoint;
    14.    
    15.     // Use this for initialization
    16.     void Start () {
    17.         lastPoint = transform.TransformDirection(Vector3.forward);
    18.         lastPoint.y = 0;
    19.     }
    20.    
    21.     // Update is called once per frame
    22.     void Update () {
    23.         Vector3 facing = transform.TransformDirection(Vector3.forward);
    24.         facing.y = 0;
    25.        
    26.         float angle = Vector3.Angle(lastPoint, facing);
    27.         if (Vector3.Cross(lastPoint, facing).y < 0)
    28.             angle *= -1;
    29.            
    30.         totalRotation += angle;
    31.         lastPoint = facing;
    32.     }
    33. }
    34.  
     
    Vicky4455 and KalyanKP like this.
  8. Talzor

    Talzor

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    May 30, 2006
    Posts:
    197
    Ah, to slow :)
     
  9. bigkahuna

    bigkahuna

    Joined:
    Apr 30, 2006
    Posts:
    5,434
    Oooo... Talzor, your code is sooo much prettier than mine! Mine is held together with band-aids and scotchtape by comparision! :D

    Thanks, I'll give it a try!
     
  10. Stephan-Tanguay

    Stephan-Tanguay

    Joined:
    Jan 27, 2011
    Posts:
    21
    Very helpful class, thanks!
     
  11. Ryan_BuzzInteractive

    Ryan_BuzzInteractive

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    Jan 25, 2017
    Posts:
    1

    Thanks for that code, it really helped me get going. I did find that if I rotated my object's parent then the calculations all went off so I needed to get my object's forward vector in local space (replacing lines 17 and 23 in your example) like this:

    Code (csharp):
    1.  
    2. Vector3 facing = transform.parent.InverseTransformDirection(transform.forward);
    3.  
    Cheers!
     
    Last edited: Jan 26, 2017
  12. EddieChristian

    EddieChristian

    Joined:
    Oct 9, 2012
    Posts:
    725
    This script it the closest I have come to finding a solution to what I need. I'm trying to get the values of the Variables TotalRotation and nrOfRotations but in all 3 Local Axis. But not sure how to modify this to get all 3. It's for a script to limit rotations on all 3 axis.
     
    Alverik likes this.
  13. Ami_2007

    Ami_2007

    Joined:
    Feb 2, 2022
    Posts:
    1
    If you want to count rotations on both sides just add Mathf.Abs to always get positive angle

    totalRotation += Mathf.Abs(angle);

    On line 30
     
  14. KalyanKP

    KalyanKP

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    Apr 7, 2021
    Posts:
    1
    Thank you.
     
  15. MelvMay

    MelvMay

    Unity Technologies

    Joined:
    May 24, 2013
    Posts:
    11,683
    15 year old thread necro. Please don't necro posts. Simply create your own. If you want to show appreciation then please use the Like button instead.
     
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