Loading Obj with OBJLoader2 to load Vertex Colors

Question

I have an .obj file which has Vertex Colors in it. That is it doesn't have seperate .mtl file for its Texture . The .obj File itself contains the color for each vertex.

I wanted to load it using three.js

I knew I can load a normal .obj file with .mtl using :

 objLoader = new THREE.OBJLoader();
        objLoader.load('meshlabshristi3.obj', function(object) {
            scene.add(object);
        });

But mine has vertex colors so I found it can be done with OBJLoader2.js so tried executing it like :

 var objLoader = new THREE.OBJLoader2();
    objLoader.load('assets/faceimage9.obj', function(object) {
        scene.add(object);
    });

But it throws errors saying

OBJLoader2.js:6 Uncaught SyntaxError: Cannot use import statement outside a module

index.html:80 Uncaught TypeError: THREE.OBJLoader2 is not a constructor
    at init (index.html:80)
    at index.html:31

Am I doing it wrong or is there any other problem . Can anyone post the exact code to load a vertex colored mesh . Thanks in advance for anyone who tried to read and solve it ...

If anyone need a vertex colored mesh to work on I had attached below.. Vertex Colored Model

For the comment below I attach this image:

Answer 1

Both OBJLoader and OBJLoader2 seem work just fine.

You just need to set material.vertexColors = true on all the materials (or all the ones that have vertex colors)

objLoader.load('assets/faceimage9.obj', function(object) {
  scene.add(object);
  object.traverse(node => {
    if (node.material) {
      node.material.vertexColors = true;
    }
  });
});

html, body {
  margin: 0;
  height: 100%;
}
#c {
  width: 100%;
  height: 100%;
  display: block;
}

<canvas id="c"></canvas>
<script type="module">
// Three.js - Load .OBJ 
// from https://threejsfundamentals.org/threejs/threejs-load-obj-auto-camera-xz.html

import * as THREE from 'https://threejsfundamentals.org/threejs/resources/threejs/r115/build/three.module.js';
import {OrbitControls} from 'https://threejsfundamentals.org/threejs/resources/threejs/r115/examples/jsm/controls/OrbitControls.js';
import {OBJLoader2} from 'https://threejsfundamentals.org/threejs/resources/threejs/r115/examples/jsm/loaders/OBJLoader2.js';

function main() {
  const canvas = document.querySelector('#c');
  const renderer = new THREE.WebGLRenderer({canvas});

  const fov = 45;
  const aspect = 2;  // the canvas default
  const near = 0.1;
  const far = 50;
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
  camera.position.set(0, 0, 0.7);

  const controls = new OrbitControls(camera, canvas);
  controls.target.set(0, 0, 0);
  controls.update();

  const scene = new THREE.Scene();
  scene.background = new THREE.Color('white');

  {
    const skyColor = 0xB1E1FF;  // light blue
    const groundColor = 0xB97A20;  // brownish orange
    const intensity = 1;
    const light = new THREE.HemisphereLight(skyColor, groundColor, intensity);
    scene.add(light);
  }

  {
    const color = 0xFFFFFF;
    const intensity = 1;
    const light = new THREE.DirectionalLight(color, intensity);
    light.position.set(5, 10, 2);
    scene.add(light);
    scene.add(light.target);
  }

  {
    const objLoader = new OBJLoader2();
    // note: this model is CC-BY-NC 4.0 from
    // here: https://sketchfab.com/3d-models/book-vertex-chameleon-study-51b0b3bdcd844a9e951a9ede6f192da8
    // by: Oleaf (https://sketchfab.com/homkahom0)
    objLoader.load('https://greggman.github.io/doodles/models/book-vertex-chameleon-study/book.obj', (root) => {
      scene.add(root);
      root.updateMatrixWorld();
      root.traverse(node => {
        if (node.material) {
          if (Array.isArray(node.material)) {
            node.material.forEach(m => m.vertexColors = true);
          } else {
            node.material.vertexColors = true;
          }
        }
      })
    });
  }

  function resizeRendererToDisplaySize(renderer) {
    const canvas = renderer.domElement;
    const width = canvas.clientWidth;
    const height = canvas.clientHeight;
    const needResize = canvas.width !== width || canvas.height !== height;
    if (needResize) {
      renderer.setSize(width, height, false);
    }
    return needResize;
  }

  function render() {

    if (resizeRendererToDisplaySize(renderer)) {
      const canvas = renderer.domElement;
      camera.aspect = canvas.clientWidth / canvas.clientHeight;
      camera.updateProjectionMatrix();
    }

    renderer.render(scene, camera);

    requestAnimationFrame(render);
  }

  requestAnimationFrame(render);
}

main();
</script>

As for the error

OBJLoader2.js:6 Uncaught SyntaxError: Cannot use import statement outside a module

If you're using ES6 modules you need to put your script in <script type="module"> script tag, and organize the files the same as they are organized in the three.js repo. Namely

+-somefolder
  |
  +-build
  |  |
  |  +-three.module.js
  |
  +-examples
    |
    +-jsm
      |
      +-controls
      | |
      | +-OrbitControls.js (if you're using this)
      |
      +-loaders
        |
        +-OBJLoader2.js

And then use import statements to load everything

<script type="module">
import * as THREE from 'somefolder/build/three.module.js';
import {OrbitControls} from 'somefolder/examples/jsm/controls/OrbitControls.js';
import {OBJLoader2} from 'somefolder/examples/jsm/loaders/OBJLoader2.js';
...

See: this answer

If you want to do it the old deprecated way with a multiple script tags instead of import then use the files from examples/js instead of examples/jsm in which case you can put them anywhere but assuming you keep them in the same place then

<script src="somefolder/build/three.min.js"></script>
<script src="somefolder/examples/js/controls/OrbitControls.js"></script>
<script src="somefolder/examples/js/loaders/OBJLoader2.js"></script>

Note it uses three.min.js not three.module.js