Pure THREE.JS template

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/three.js/107/three.min.js"></script>
<script src="http://threejs.org/examples/js/controls/OrbitControls.js"></script>

JavaScript

var scene, renderer, camera, controls;

init();
animate();

function init() {
  renderer = new THREE.WebGLRenderer({
    antialias: true
  });
  var width = window.innerWidth;
  var height = window.innerHeight;

  renderer.setSize(width, height);

  document.body.appendChild(renderer.domElement);

  scene = new THREE.Scene();

  camera = new THREE.PerspectiveCamera(60, width / height, 0.01, 10000);
  camera.position.y = 16;
  camera.position.z = 40;
  camera.lookAt(new THREE.Vector3(0, 0, 0));
  
  var controls = new THREE.OrbitControls( camera );

  var material = new THREE.LineBasicMaterial({
    color: 0xAAFFAA
  });

  // crosshair size
  var x = 0.01,
    y = 0.01;

  var geometry = new THREE.Geometry();

  // crosshair
  geometry.vertices.push(new THREE.Vector3(0, y, 0));
  geometry.vertices.push(new THREE.Vector3(0, -y, 0));
  geometry.vertices.push(new THREE.Vector3(0, 0, 0));
  geometry.vertices.push(new THREE.Vector3(x, 0, 0));
  geometry.vertices.push(new THREE.Vector3(-x, 0, 0));

  var crosshair = new THREE.Line(geometry, material);

  // place it in the center
  var crosshairPercentX = 50;
  var crosshairPercentY = 50;
  var crosshairPositionX = (crosshairPercentX / 100) * 2 - 1;
  var crosshairPositionY = (crosshairPercentY / 100) * 2 - 1;

  crosshair.position.x = crosshairPositionX * camera.aspect;
  crosshair.position.y = crosshairPositionY;
  crosshair.position.z = -0.3;

  camera.add(crosshair);
  scene.add(camera);

  var gridXZ = new THREE.GridHelper(100, 10);
  scene.add(gridXZ);
}

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