How to Use Quaternion in Unity?

shakiroslann -

Quaternions are an extension of complex numbers and can be used to represent 3D rotations, spatial translations, and scaling. Invented by Sir William Rowan Hamilton in 1843, these numbers are not easy to understand intuitively. With all honesty, I still don't fully know how it works.

However, in Unity, we can handle the rotation without having to understand them fully. Now, Let’s look at some useful things we can do with Unity Quaternion API

1. Slerp

public static Quaternion Slerp(Quaternion a, Quaternion b, float t);

Slerp is a spherical interpolation between quaternions a and b by the ratio of t. The parameter t is clamped in between [0, 1].

Opening & closing the door using the slerp method.
The door is closed when _t is 0.
The door is half open when _t is 0.5.
The door is fully open when _t is 1.

2. LookRotation

public static Quaternion LookRotation(Vector3 forward, Vector3 upwards = Vector3.up);

Creates a rotation with the specified direction to look in and the vector that defines in which direction up is.

  • forward: direction to look in
  • upwards : vector that defines in which direction up is
A rocket is looking in the direction of the cube.

3. Quaternion.Euler

public static Quaternion Euler(float x, float y, float z);

Returns a rotation that rotates z degrees around the z-axis, x degrees around the x-axis, and y degrees around the y-axis; applied in that order. We can set a new rotation to a game object with this method.

Turret barrels are rotating on their x-axis between 0 & 30 degrees using Quaternion.Euler method.

4. Quaternion.RotateTowards

public static Quaternion RotateTowards(Quaternion from, Quaternion to, float maxDegreesDelta);

Creates a rotation that rotates from one direction to another direction maxDegreesDelta as an angular step towards the target.

A gun is rotating toward the target using Quaternion.RotateTowards method.

5. Rotate a vector

Vector3 rotation = Quaternion.Euler(0,_angle,0) * _rotatingObject.right * _radius;

Multiplying a vector with Quaternion.

A sphere is orbiting around the bigger sphere by multiplying its right vector with Quaternion.