create = (polygons) => {
  if (polygons === undefined) {
    polygons = [] // empty contents
  }
  return {
    polygons,
    transforms: mat4.create()
  }
}
Create a new 3D geometry composed of the given polygons.
@param {Array} [polygons] - list of polygons, or undefined
@returns {geom3} a new geometry
@alias module:modeling/geometries/geom3.create