code: function centerMesh (mesh) {
    var bb = boundingBox(mesh.positions)
  
    var _translate = [
      -0.5 * (bb[0][0] + bb[1][0]),
      -0.5 * (bb[0][1] + bb[1][1]),
      -0.5 * (bb[0][2] + bb[1][2])
    ]
    var translate = mat4.create()
    mat4.translate(translate, translate, _translate)
    mesh.positions = tform(mesh.positions, translate)
  }
docs: center the rabbit mesh to the origin.