Merge Geometries

Let's import the BufferGeometryUtils.

import { BufferGeometryUtils } from 'https://unpkg.com/three/examples/jsm/utils/BufferGeometryUtils.js';

We can create a simple object that will hold each material group.

class MaterialGroup {
  constructor(material, bufferGeometries) {
    this.material = material;
    this.bufferGeometries = bufferGeometries;
  }
}

W.I.P