如何在 Three.js 上覆盖 HTML 文本/按钮？

var buttons = document.getElementsByTagName("button");
for (let i = 0; i < buttons.length; i++) {
  buttons[i].addEventListener("click", onButtonClick, false);
};

function onButtonClick(event) {
  alert(event.target.id);
}

var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);

var renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

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

var geometry = new THREE.BoxGeometry(1, 1, 1);
var material = new THREE.MeshBasicMaterial({
  color: 0x00ff00,
  wireframe: true
});
var cube = new THREE.Mesh(geometry, material);
scene.add(cube);

camera.position.z = 5;

var animate = function() {
  requestAnimationFrame(animate);
  renderer.render(scene, camera);
};

animate();

body {
  overflow: hidden;
  margin: 0;
}

.ui {
  position: absolute;
}

button{
  margin: 20px;
}

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

<div style="width:100%;height:50px;text-align: center; color:white;" class="ui">Info header</div>
<button style="top:0" id="fire" class="ui">Fire</button>
<button style="bottom:0" id="spell" class="ui">Spell</button>
<button style="right:0" id="health" class="ui">Health</button>
<button style="right:0; bottom:0;" id="shield" class="ui">Shield</button>