1

So for assign rotation to gameobject with euler angles as input values i can do 2 ways:

  1. transform.localRotation = Quaternion.Euler(x, y, z);

  2. transform.localEulerAngles = new Vector3(x, y, z);

What way better and why (at performance point of view)?

2

Both lines do the exact same thing: converting 3 euler angles floats into a quaternion. Efficiency is completely irrelevant here. Both only use value types (float, Vector3, Quaternion) so no garbage should be created by non of them. “localEulerAngles” is there to simplify getting / setting eulerangles.

3

They’re both pretty identical from a performance point of view.
I’ve ran a test on my notebook with 10.000 assignments in one frame on keydown. This is, in most cases, far away from the common usage unless you’ve got a huge project in which this happens alot, like thousands of times.

It yielded 24-26 milliseconds for the first one. The second one yielded 22 milliseconds frequently, in a few cases 23 milliseconds. Tests were repeated a few times just to be sure.

Regarding the amount of assigments, this isn’t much of a difference, so to say they’re pretty much equal performance-wise (in average for one call: 0,0025 milliseconds = 2.5 microseconds for the first, 2.2 microseconds for the second). This is really nothing to worry about, use the one that you like the most.

An assumption:

The difference could be that the first one does an extra calculation in the property:

  • calculates a quaternion from the euler angles first in order to get the rotation
  • assigns the quaternion to the rotation
  • euler angles are now recalculated in the transform.localRotation property from the new rotation because they might not be stored but calculated on the fly - but that’s an implementation details that i don’t know

The second one:

  • just assigns the euler angles
  • recalculates the quaternion in the localEulerAngles property

So if it’s really implemented like that, you’d save one calculation of euler angles.