How to get the y angle between 2 vectors in Three.js?

Question

In Three.js I have 2 3d vectors and I want to find the x-axis and y-axis angle between them.

For the x-axis I found this

toDegrees(atan2(A.z, A.y) - atan2(B.z, B.y))

from The X angle between two 3D vectors?

which works, but for y-axis, I am trying

toDegrees(atan2(A.z, A.x) - atan2(B.z, B.x))

but it gives me the wrong value. How can I fix this?

Thanks

Answer 1

You can use Vector3.angleTo directly, it will give you the angle in radians, as usual to math functions, here I printing it in degrees (multiplying by 180 degrees/pi rad= 1)

// notice that v1 is pointing to the x-axis direction.
const v1 = new THREE.Vector3(10,0,0);
const v2 = new THREE.Vector3(3,3,0);
const v3 = new THREE.Vector3(0, 50, 23);
// Alngle between v1 and v2
console.log(v1.angleTo(v2)*180/Math.PI)
// The operation is comutative
console.log(v2.angleTo(v1)*180/Math.PI)
// An example at 90 degree
console.log(v1.angleTo(v3)*180/Math.PI)

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r128/three.min.js"></script>

This makes it possible to find angles to any direction, if you want angle to a plane for instance, it is given by ans(a - 90) where a is the angle in degrees to the normal vector of the plane.