How to use Euler angles to rotate an object ?

Here are my suggested "rules" for how you deal with eularAngles in this situation:

• Never read eulerAngles. Consider them write-only.

• Keep your own Vector3 that represents the current rotation.

• Never assign to an individual eulerAngles component (like eulerAngles.y). Always assign a Vector3 to eulerAngles.

Here is a simple script:

 #pragma strict
  
 public var speed = 1.0;
 private var v3To = Vector3(2025,0,0);
 public var v3Current = Vector3(0,0,0);
  
 function Start() {
    transform.eulerAngles = v3Current; 
 }
  
 function Update () {
     v3Current = Vector3.Lerp(v3Current, v3To, Time.deltaTime * speed);
     transform.eulerAngles = v3Current; 
 }

Note changes in rotation are made to v3Current and then v3Current is assigned to Transform.eulerAngles. This way v3Current will always reflect one euler angle representation of the 'physical' rotation. But note that the actual eulerAngles value will not necessarily match v3Current. But they will both represent the same 'physical' rotation.

Quaternion.Lerp() will select the shortest distance between two rotations, so that will not work for you. Vector3.Lerp() will literally interpret the values passed. So if you want to rotate the long way from 41 to 0, you have to change the values so the Lerp() walks that way. In this example, you would set the final rotation to 360 rather than 0.

Note in playing these games, you typically want to normalize the v3Current values back into a standard range (0 to 360 or perhaps -180 to 180) before calculating and setting the new destination angle.