constructor(body, physicsBody, options) {
    this.body = body;
    this.physicsBody = physicsBody;
    this.barnesHutTree;
    this.setOptions(options);
    this._rng = Alea("BARNES HUT SOLVER");

    // debug: show grid
    // this.body.emitter.on("afterDrawing", (ctx) => {this._debug(ctx,'#ff0000')})
  }
@param {object} body
@param {{physicsNodeIndices: Array, physicsEdgeIndices: Array, forces: {}, velocities: {}}} physicsBody
@param {object} options