Quaternion.Equals

Parameters

Returns

bool true if the quaternion components (x, y, z, w) are exactly equal.

Description

Performs exact binary comparison of each Quaternion component (x, y, z, w).

The key comparison characteristics:

• Exact copies: Returns true when quaternions are identical copies.
• Floating-point precision: Returns false even for tiny differences due to floating-point arithmetic.
• Mathematically equivalent rotations: Returns false for rotations that represent the same orientation but have different component values.

For practical rotation comparison, consider using the == operator instead, which uses dot product with tolerance for approximate equality.

using UnityEngine;

public class QuaternionEqualsExample : MonoBehaviour
{ 
    void Start()
    {
        // Exact copies - Equals() returns true
        Quaternion q1 = Quaternion.identity;
        Quaternion q2 = q1;
        Debug.Log($"Exact copies - Equals(): {q1.Equals(q2)}"); // True
        
        // Small floating point differences - Equals() returns false
        Quaternion q3 = Quaternion.Euler(90f, 0f, 0f);
        Quaternion q4 = Quaternion.Euler(90.0001f, 0f, 0f);
        Debug.Log($"Small difference - Equals(): {q3.Equals(q4)}"); // False
        Debug.Log($"Small difference - == operator: {q3 == q4}");   // True (tolerance-based)
        
        // Combine both methods for robust comparison
        Debug.Log($"Combined check: {q3.Equals(q4) || (q3 == q4)}"); // True
    }
}