ELI5: Explain Like I'm 5

Quaternions and spatial rotation

Okay kiddo, let's talk about quaternions and spatial rotation! Do you know what rotation is? It's when something turns or spins around an axis or point. Like when you spin a top around its handle, it's rotating.

Now imagine a ball that's rotating in space, and you want to describe how it's rotating. You can use something called a quaternion to do that.

A quaternion is a way of storing information about how an object is rotated in space. It contains four numbers: w, x, y, and z. These four numbers tell you the angle of rotation and the axis around which the object is rotating.

Let's say you want to rotate the ball by 90 degrees around the x-axis. You can use a quaternion to describe how to do that. The quaternion would look like this: (cos(45), sin(45), 0, 0). The w value is cos(45), which is the angle of rotation. The x, y, and z values are 0 because the rotation is only around the x-axis.

So how does this all work? Well, when you apply a quaternion to an object, it changes its orientation in space. The object is rotated by the angle specified in the w value around the axis specified by the x, y, and z values.

It may seem a bit confusing, but quaternions are actually a really useful way of describing rotations because they avoid some of the problems that other methods have. For example, with Euler angles, if you rotate an object in one direction and then another, the order of the rotations matters and can affect the final orientation. With quaternions, you can perform multiple rotations in any order and get the same final orientation.

So there you go, kiddo, that's a basic explanation of quaternions and spatial rotation. Isn't it cool how math can help us understand how things move and turn in space?