How to change two rotation axes in Unity without affecting the third?

Question

I have a GameObject in Unity and I need to change its X and Z rotation without doing anything with the Y, as that would mess up everything.
Note that this sets the Y rotation to 0 and I don't want that (I want it to let it be be what it already is), so this isn't any good:

gameObject.transform.rotation = Quaternion.Euler(someNewAngle, 0f, someNewAngle);

What should I do?

In the most general sense this isn't possible — it's in the nature of 3D rotation that some combinations of two different axes can accomplish rotations in a third, as demonstrated in this answee. Euler angles tend to mislead us by pretending there's a natural separation between the axes as there is with translation, but it's just a convenient fiction. That said, we can probably get the rotation behaviour you need if you can describe what you want in some other terms. What are you rotating, and how should it behave? — DMGregory, Oct 27 '18 at 12:07
I don't know why you want to do this, but maybe transform.Rotate (change the direction by a relative amount) or transform.LookAt (yaw and pitch to a point while keeping alligned with the horizon) might be useful for your use-case. — Philipp, Nov 13 '18 at 10:21

score 1 · Accepted Answer · 2018-10-29T12:35:29.203

1

Just take the previous value of the Y rotation using transform.rotation.eulerAngles.

So your code would look like this:

var yRotation = gameObject.transform.rotation.eulerAngles.y;
gameObject.transform.rotation = Quaternion.Euler(someNewAngle, yRotation, someNewAngle);

edited Oct 29 '18 at 12:35

answered Oct 27 '18 at 10:41

How to change two rotation axes in Unity without affecting the third?

1 Answers1