Unexpected ShapeGeometry with projection and quaternion

by Peque

HTML

<script src="https://threejs.org/build/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>

CSS

body {
  overflow: hidden;
  margin: 0;
}

JavaScript

var renderer, controls, scene, camera;

init();

function init() {

    // Scene
    scene = new THREE.Scene();
    scene.background = new THREE.Color(0xb0b0b0);

    // Camera
    camera = new THREE.PerspectiveCamera(30, window.innerWidth / window.innerHeight, 1, 1000);
    camera.position.set(0, 0, 400);
    camera.up.set(0, 0, 1);

    // Light
    var ambientLight = new THREE.AmbientLight(0xcccccc, 0.2);
    scene.add(ambientLight);

    // Helpers
    var helpers = new THREE.Group();
    var grid = new THREE.GridHelper(200, 10);
    grid.rotation.x = Math.PI / 2;
    var axis = THREE.AxisHelper(100);
    helpers.add(grid);
    helpers.add(axis);
    scene.add(helpers);

    // Renderer
    renderer = new THREE.WebGLRenderer({ antialias: true });
    renderer.setPixelRatio(window.devicePixelRatio);
    renderer.setSize(window.innerWidth, window.innerHeight);
    document.body.appendChild(renderer.domElement);

    // Controls
    controls = new THREE.OrbitControls(camera, renderer.domElement);

    // Event listeners
    controls.addEventListener("change", render, false);

    // Draw projected mesh
    var points = [
        new THREE.Vector2(-20, 0),
        new THREE.Vector2(-20, -20),
        new THREE.Vector2(20, -20),
        new THREE.Vector2(20, 20),
        new THREE.Vector2(0, 20),
        new THREE.Vector2(0, 0),
        new THREE.Vector2(-20, 0),
    ];
    var plane = new THREE.Plane().setFromNormalAndCoplanarPoint(
        new THREE.Vector3(0.7071067811865475, 0, 0.7071067811865475),
        new THREE.Vector3(20, 0, 0)
    );
    var mesh = projectPoints(points, plane);
    scene.add(mesh);

    // Render
    render();
}

function projectPoints(points, plane) {
    var projectedPoints = [];
    const upDirection = new THREE.Vector3(0, 0, 1);
    points.forEach(p => {
        const r = new THREE.Ray(new THREE.Vector3(p.x, p.y, 0.0), upDirection);
        let intersection = new THREE.Vector3();
        r.intersectPlane(plane, intersection);
      ...