Rotate a Vector3 direction

Question

How can i rotate a Vector3 direction 45 degrees along the y axis? So a Vector3(1,0,0) for example, would become Vector3(0.5,0,0.5).

And i cant use Transform.RotateAround, or any other Transform methos. As i am not applying this Vector3 directly to a object.

Answer 1

Best Answer

Answer by Jessy · Feb 08, 2011 at 08:04 PM

http://unity3d.com/support/documentation/ScriptReference/Quaternion.AngleAxis.html

vector = Quaternion.AngleAxis(-45, Vector3.up) * vector;

That's a general case. For rotation around a world axis, it's faster/easier:

vector = Quaternion.Euler(0, -45, 0) * vector;

For (1,0,0), this results in (sqrt(.5), 0, sqrt(.5)), not (.5,0,.5), by the way. The length of the rotated vector stays constant. To achieve a squared hypotenuse of 1, you add .5, 0, and .5, not .25, 0, and .25, which would shorten your vector.

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Mattivc · Feb 09, 2011 at 08:04 PM 0

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Thanks, this works great.

Jessy · Feb 09, 2011 at 09:47 PM 2

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Glad to hear it. Rotate those vectors like they were on the Witches' Wheel!

beneon · Sep 14, 2014 at 02:34 PM 0

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really thanks a lot

Thaoren · Nov 02, 2018 at 01:47 AM 3

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Thanks! Worked great.

One thing to note is that you cannot do:

 vector = vector * Quaternion.AngleAxis(-45, Vector3.up);

and must do

 vector = Quaternion.AngleAxis(-45, Vector3.up) * vector;

as there are some reasons internal to Unity.

tormentoarmagedoom · Jan 29 at 09:35 PM 3

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Good question, good answer

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Answer 2

Answer by elhispano · Feb 10, 2013 at 03:00 PM

That operation is dependent on the order. rotatedVector = Quaternion vector OK rotatedVector = vector Quaternion won´t works and will launch a compiler error

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beneon · Sep 14, 2014 at 02:35 PM 0

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ok, Got it.

Rotate a Vector3 direction

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