Rotate an object so its x axis would align with a vector

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It's 3 am, I'll try to be clear... transform.position is the vector start point, let's say A(x,y,z). B(a,b,c) is the end of the vector. Consider this vector as a line in space, direction is irrelevant. Now, how should I rotate the object I have so its x axis would align with the vector AB? I mean, through code, using c#. If I know A and B, how would I calculate the transform.rotate for the object? Thank you in advance.

Answer 1

Best Answer

Answer by robertbu · Dec 09, 2014 at 01:13 AM

 Vector3 v = B - A;
 Quaternion q = Quaternion.FromToRotation(transform.right, v);
 transform.rotation = q * transform.rotation;

Or simpler:

  Vector3 v = B - A;
  transform.rotation = Quaternion.FromToRotation(Vector3.right, v);

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PhoenixBlackReal · Dec 09, 2014 at 01:21 AM 0

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You're awesome! Thank you, I'm going to crash in my bed now UwU But you, however, have an amazing day!

Fe0dor · Sep 08, 2020 at 09:14 PM 0

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6 years later and I too found myself in this situation... You saved my night

mscottveach · Sep 09, 2021 at 06:59 AM 0

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Exactly one year to the day later, I, too, find myself in the situation.

IsitaSpider · May 04 at 05:39 PM 0

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Still perfect in 2022, really helpful, thank you !

Answer 2

Answer by David_Biggs · Dec 09, 2014 at 02:23 AM

transform.right = B-A;

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ShawnFeatherly · Sep 21, 2017 at 11:56 PM 0

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Nice shortcut, and easier to understand than setting transform.rotation to some Quaternion.LookRotation() that would get the angle right.

Answer 3

Answer by Vitaly-Abilevich · Sep 13, 2017 at 11:16 PM

Thanks, this works perfect, is there a way to add a Linear Interpolation?

 Vector3 v = go.transform.position - transform.position;
 Quaternion q = Quaternion.FromToRotation(-transform.up, v);
 // Changed next line for the last one
 //transform.rotation = q * transform.rotation;
 transform.rotation = Quaternion.Lerp(transform.rotation, q, Time.deltaTime * alignSpeed);

And with this change weird stuff happens

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Rotate an object so its x axis would align with a vector

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