Quaternion.identity

Description

The identity rotation (Read Only).

This property represents zero rotation. For example, if you assign Quaternion.identity to a transform's world coordinates, the transform's axis (right, up, forward) aligns with the world axis (x, y, z). If you assign it to the transform's local rotation, the transform aligns with the axis of its parent. Key property characteristics:

* Setting transform.rotation = Quaternion.identity aligns the object with the world axes.

* Setting transform.localRotation = Quaternion.identity sets the object's local rotation to match the parent's orientation (no local rotation relative to the parent).

* Multiplying by Quaternion.identity has no effect.

Common use cases:

* Instantiate objects with neutral rotation: Instantiate(prefab, position, Quaternion.identity).

* Reset object rotation to world-aligned state.

* Use as a starting point for rotational calculations.

using UnityEngine;

public class QuaternionIdentityExample : MonoBehaviour
{
    public Transform parentObject;
    public Transform childObject;

    void Start()
    {
        // Quaternion.identity represents zero rotation relative to world coordinate system, aligned with world axes.
        transform.rotation = Quaternion.identity;

        // Demonstrate the difference between world rotation and local rotation:
        if (parentObject != null && childObject != null)
        {
            // Set child to identity rotation
            childObject.rotation = Quaternion.identity;
            
            // Child is aligned with world axes, not current parent's rotated axes.
            Debug.Log($"Child rotation: {childObject.rotation}");
            Debug.Log($"Parent rotation: {parentObject.rotation}");
            
            // To align with current parent axes, use:
            // childObject.localRotation = Quaternion.identity;
        }
    }
}