JSFiddle - React, Tailwind, and code Playground

JavaScript

var camera, scene, renderer, projector, geometry, material, mesh;

init();
animate();

function init() {

    scene = new THREE.Scene();

    camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 1, 10000);
    camera.position.z = 500;
    scene.add(camera);
    
    geometry = new THREE.CubeGeometry(20, 20, 20);
    material = new THREE.MeshNormalMaterial();

    mesh = new THREE.Mesh(geometry, material);
    mesh.position.set(10, 10, 10);
    scene.add(mesh);

    renderer = new THREE.CanvasRenderer();
    renderer.setSize(window.innerWidth, window.innerHeight);
    renderer.domElement.addEventListener('mouseup', onDocumentMouseUp, false);

    projector = new THREE.Projector();

    document.body.appendChild(renderer.domElement);
}

function getMousePosition(clientX, clientY) {
    var mouse2D = new THREE.Vector3();
    var mouse3D = new THREE.Vector3();
    mouse2D.x = (clientX / window.innerWidth) * 2 - 1;
    mouse2D.y = -(clientY / window.innerHeight) * 2 + 1;
    mouse2D.z = 0.5;
    mouse3D = projector.unprojectVector(mouse2D.clone(), camera);
    return mouse3D;
    //var vector = new THREE.Vector3(
    //( clientX / window.innerWidth ) * 2 - 1,
    //- ( clientY / window.innerHeight ) * 2 + 1,
    //0.5 );

    //projector.unprojectVector( vector, camera );
    //var dir = vector.sub( camera.position ).normalize();
    //var distance = - camera.position.z / dir.z;
    //var pos = camera.position.clone().add( dir.multiplyScalar( distance ) );
    //return pos;
}

function onDocumentMouseUp(event) {
    event.preventDefault();

    var mouse3D = getMousePosition(event.clientX, event.clientY);
    console.log(mouse3D.x + ' ' + mouse3D.y + ' ' + mouse3D.z);
}

function animate() {
    requestAnimationFrame(animate);
    render();
}

function render() {
    renderer.render(scene, camera);
}