How to update vertex of mesh in three.js after rotation? - three.js

Question

I'm working in 1.4.2 three.js version. I rotate mesh and want to get it updated vertexes. Here is my codepen: https://codepen.io/DYDOI-NSK/pen/mdxLpoB?editors=1012
Here is my code:
I have a function at 37 line, that allow me create planes.
/* generatePlanes - function that create planes.
* #param data - config for creating planes, must contain name,
* count of creating planes, width and height.
* #return planeHolder - array with created planes.
*/
let generatePlanes = (data) => {
let planeHolder = [];
for (let i = 0; i < data.count; i++) {
let geometry = new THREE.PlaneGeometry( data.width, data.height );
let material = new THREE.MeshBasicMaterial( {color: new THREE.Color('#cea6a6'), side: THREE.DoubleSide} );
let plane = new THREE.Mesh( geometry, material );
plane.name = data.name;
plane.isConnected = false;
planeHolder.push(plane);
}
return planeHolder;
}
I created two planes with generatePlanes function at 53 line
// Creating 2 planes
let planes = generatePlanes({
name: 'centerPlane',
count: 2,
width: 30,
height: 30,
});
At lines 63-67 I described problem. I logged plane.geometry.attributes.position.array(here contains vertexes position of mesh) before and after rotation.
// Check verticies before rotating
console.log(planes[0].geometry.attributes.position.array);
// Rotate first plane with rotateX method
planes[0].rotateX(Math.PI / 4);
// Check verticies after rotating
console.log(planes[0].geometry.attributes.position.array);
Result of logs:
Before rotation:
Float32Array(12)
0: -15
1: 15
2: 0
3: 15
4: 15
5: 0
6: -15
7: -15
8: 0
9: 15
10: -15
11: 0
After rotation:
Float32Array(12)
0: -15
1: 15
2: 0
3: 15
4: 15
5: 0
6: -15
7: -15
8: 0
9: 15
10: -15
11: 0
Vertexes having the same position, i need to update them, but i don't know how.

Answer 1

Since the goal is to calculate the angle between two planes, a better solution than looking at the position attribute is to create a vector representing the plane and apply the same rotation to the vector. There is already a solid answer for this here: https://stackoverflow.com/a/45309019/4536210
As to why the position attribute doesn't change when rotating, this is because the rotation is applied to the Mesh while the Geometry is always kept intact. The position attribute represents an intrinsic property of the geometry, representing the arrangement of its vertices in space, they're never modified by transforming the object.