Coordinates for greedy meshing

export function get_mesh(is_faced){
  var mesh = {};
  mesh.vertices = [];
  mesh.normals = [];
  mesh.uvs = [];
  mesh.indices = [];
  var faces;
  /*         +--------+
   *       x/        /|
   *       /        / |
   *      +--------+  |
   *     ^|   z->  |  |
   *     ||        |  +
   *     y|        | /
   *      |        |/
   *      +--------+
   */
  for(let x=0;x<=cell_size;x++){
    faces = get_faces(function(y,z){return is_faced(x, y, z, [-1,0,0]);});
    for(let i=0;i<faces.length;i++){
      add_face_x(mesh, x, faces[i]);
    }
  }
  for(let y=0;y<=cell_size;y++){
    faces = get_faces(function(x,z){return is_faced(x,y,z, [0,-1,0]);});
    for(let i=0;i<faces.length;i++){
      add_face_y(mesh, y, faces[i]);
    }
  }

  for(let z=0;z<=cell_size;z++){
    faces = get_faces(function(x,y){return is_faced(x,y,z, [0,0,-1]);});
    for(let i=0;i<faces.length;i++){
      add_face_z(mesh, z, faces[i]);
    }
  }
  return mesh;
}