ScriptReference/Quaternion

[giscus[bot]]

ScriptReference/Quaternion

https://docs.unity3d.com/ScriptReference/Quaternion.html

[zORg-alex]

• Quaternion(0,0,0,0) is invalid, Quaternion.identity is the initial, zero rotation. Under the hood it's a Vector4 and is supposed to have margin = 1f since it's a 4D sphere coordinate
• Rotate vector with a quaternion:

Vector3 worldForward = rotation * Vector3.forward;

• Multiply two Quaternions to get a sum of forations.
• Quaterion.Inverse(rotation) to get backwards rotation if you need unrotate something.
• To get a rotation from A rotation to B rotation

Quaternion diff = Quaternion.Inverse(A) * B;

Here is a script that shows all possibilities to help you wrap your head around this concept:

#if UNITY_EDITOR
using System;
using UnityEditor;
#endif
using UnityEngine;

public class QuaterionTest : MonoBehaviour
{
	public Quaternion A = Quaternion.identity;
	public Quaternion B = Quaternion.identity;

#if UNITY_EDITOR
	[CustomEditor(typeof(QuaterionTest))]
	public class QuaterionTestInspector : Editor
	{
		public override void OnInspectorGUI()
		{
			base.OnInspectorGUI();
		}

		private void OnEnable() => SceneView.duringSceneGui += OnSceneGUI;
		private void OnDisable() => SceneView.duringSceneGui -= OnSceneGUI;

		private void OnSceneGUI(SceneView view)
		{
			var t = target as QuaterionTest;

			Handles.DrawLine(t.transform.position, Vector3.zero);

			var pos = t.transform.position;
			Handles.Label(pos, "A");
			Handles.DoPositionHandle(pos, t.transform.rotation * t.A);

			pos += t.transform.right;
			Handles.Label(pos, "B");
			Handles.DoPositionHandle(pos, t.transform.rotation * t.B);

			pos += t.transform.right;
			Handles.Label(pos, "A * B");
			Handles.DoPositionHandle(pos, t.transform.rotation * t.A * t.B);

			pos += t.transform.right;
			Handles.Label(pos, "inv(A) * B");
			Handles.DoPositionHandle(pos, t.transform.rotation * Quaternion.Inverse(t.A) * t.B);

			pos += t.transform.right;
			Handles.Label(pos, "A * inv(B)");
			Handles.DoPositionHandle(pos, t.transform.rotation * t.A * Quaternion.Inverse(t.B));
		}
	}
#endif
}