rough translation of three.js hello world into ocaml (js_of_ocaml)

app.ml

open Js_of_ocaml

let main () =
  let doc = Dom_html.document in
  let inner_width =
    Js.Optdef.get Dom_html.window##.innerWidth (fun () -> 1000)
  in
  let inner_height =
    Js.Optdef.get Dom_html.window##.innerHeight (fun () -> 500)
  in
  let three = Js.Unsafe.global##._THREE in
  let scene_constr = three##._Scene in
  let perspective_camera_constr = three##._PerspectiveCamera in
  let renderer_constr = three##.WebGLRenderer in
  let scene = new%js scene_constr in
  let camera =
    (new%js perspective_camera_constr) 75
      (inner_width / inner_height) 0.1 1000
  in
  camera##.position##.z := 4;
  let renderer =
    let args = Js.Unsafe.js_expr "{ antialias: true }" in
    (new%js renderer_constr) args
  in
  let cube =
    let geometry_constr = three##._BoxGeometry in
    let material_constr = three##._MeshBasicMaterial in
    let mesh_constr = three##._Mesh in
    let geometry = (new%js geometry_constr) 1 1 1 in
    let material =
      let args = Js.Unsafe.js_expr "{ color: \"#433F81\" }" in
      (new%js material_constr) args
    in
    let cube = (new%js mesh_constr) geometry material in
    cube
  in
  let requestAnimationFrame f =
    Js.Unsafe.fun_call (Js.Unsafe.js_expr "requestAnimationFrame")
      [| Js.Unsafe.inject f |]
  in
  let rec render () =
    let () = requestAnimationFrame render in
    cube##.rotation##.x := cube##.rotation##.x +. 0.01;
    cube##.rotation##.y := cube##.rotation##.y +. 0.01;
    renderer##render scene camera;
  in
  let _ = renderer##setClearColor (Js.string "#000000") in
  let _ = renderer##setSize inner_width inner_height in
  Dom.appendChild doc##.body renderer##.domElement;
  let () = scene##add cube in
  render ()

let () = main ()