Set a RectTranform's pivot without changing its position

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Is there a way to change a RectTransform's pivot point without changing its position? If not, does someone know the math I would have to do to simulate this behavior? Thanks in advance!

Answer 1

Best Answer

Answer by jmorhart · Jul 30, 2015 at 05:35 PM

Well, I managed to figure this one out on my own. Implemented as an extension method of the RectTransform class. Currently only works properly for XY axis-aligned objects.

     public static void SetPivot(this RectTransform rectTransform, Vector2 pivot)
     {
         if (rectTransform == null) return;
 
         Vector2 size = rectTransform.rect.size;
         Vector2 deltaPivot = rectTransform.pivot - pivot;
         Vector3 deltaPosition = new Vector3(deltaPivot.x * size.x, deltaPivot.y * size.y);
         rectTransform.pivot = pivot;
         rectTransform.localPosition -= deltaPosition;
     }

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KwahuNashoba · Dec 12, 2016 at 04:22 PM 0

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Thanks man! This does not make sense AT ALL! :D But it works. I have spent whole week trying to assign x,y position of RectTransform, also anchoredPosition and it never came to my $$anonymous$$d that it was this simple :)

Reyan62 · Feb 06, 2017 at 06:30 PM 0

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Awesome, I needed to do just this and was able to drop in your solution with no problems. Thanks!

dugsteen · Jul 12, 2017 at 04:42 PM 4

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Note: If you're changing scale at all, you'll need to incorporate that as well:

 var scale = rectTransform.localScale;

...

 var deltaPosition = new Vector3(
   deltaPivot.x * size.x * scale.x, 
   deltaPivot.y * size.y * scale.y);

Roywise · Sep 11, 2017 at 01:40 PM 0

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Do you know how to implement this method when the RectTransform has been rotated as well? It seems to be a bit more complex and I can't figure it out.

Issun · Sep 17, 2017 at 11:30 AM 0

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+Props to you dude, solid solution and awesome of you to put it in a method for people to copy paste.

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Answer 2

Answer by LiterallyJeff · Aug 24, 2018 at 03:20 PM

Here is a cleaned up version of previous commenters' extension function, which supports scaling & rotation.

 /// <summary>
 /// Set pivot without changing the position of the element
 /// </summary>
 public static void SetPivot(this RectTransform rectTransform, Vector2 pivot)
 {
     Vector3 deltaPosition = rectTransform.pivot - pivot;    // get change in pivot
     deltaPosition.Scale(rectTransform.rect.size);           // apply sizing
     deltaPosition.Scale(rectTransform.localScale);          // apply scaling
     deltaPosition = rectTransform.rotation * deltaPosition; // apply rotation
     
     rectTransform.pivot = pivot;                            // change the pivot
     rectTransform.localPosition -= deltaPosition;           // reverse the position change
 }

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eses · Aug 24, 2018 at 03:47 PM 0

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@ jeffreyschoch - This is great! Thanks for sharing.

jomalomal · Feb 06, 2019 at 06:29 PM 0

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To get this to work I had to replace rectTransform.rotatation with rectTransform.transform.localRotation

Answer 3

Answer by wck19870829 · Mar 14, 2019 at 08:52 AM

     public static void SetPivot(RectTransform target, Vector2 pivot)
     {
         if (!target) return;

         var offset=pivot - target.pivot;
         offset.Scale(target.rect.size);
         var wordlPos= target.position + target.TransformVector(offset);

         target.pivot = pivot;
         target.position = wordlPos;
     }

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InteractiveScape · Jan 24, 2020 at 09:34 AM 0

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Thanks! That was the only solution that worked in my case. Not sure why the previous solutions caused problems in my setup...

Set a RectTranform's pivot without changing its position

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