Constraining Rotation

Templates & Documentation Documentation
1

Is there a way to constrain the rotation of one or more axis so that it can only rotate up to a certain amount? For example, allowing the Y axis to only rotate to 30 or -30 degrees?
I wasn’t able to find anything that looked like this in the scripting reference. Any ideas?

2

I don’t think that there’s anything super-elegant [edit: I was wrong.], but you can always just write

if (transform.rotation.y > 30)
{
transform.rotation.y = 30;
}
if (transform.rotation.y < -30)
{
transform.rotation.y = -30;
}

It isn’t beautiful, but it’ll do the job.

3

transform.rotation.y = Mathf.Clamp(transform.rotation.y, -30.0, 30.0);

4

This is almost true: you should use transform.eulerAngles though.

transform.rotation.y would modify the 2nd component in the rotation quaternion, which does not have any intuitive effect.

5

Thanks for your responses. The script with eulerAngles works but I am getting some choppy motion. I have other things affecting the physics of the objects though, so I will keep playing with it and see if I can smooth things out.
Thanks again for your help.

6

If the object has a rigidbody you are going to have to use rigidbody.AddForce(). For doing stuff like this ForceMode.VelocityChange is your freind. This constrains a rigidbody on it’s y axis:

relativeAngularVelocity = transform.InverseTransformPoint(rigidbody.angularVelocity);
relativeAngularVelocity.y = 0;
newAngularVelocity = transform.TransformPoint(relativeAngularVelocity);
difference = newAngularVelocity - rigidbody.angularVelocity;
rigidbody.AddTorque(difference, ForceMode.VelocityChange);
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