options = pycolmap.BundleAdjustmentOptions()
pycolmap.bundle_adjustment(reconstruction, options)

#prior: reconstruction folder sfm_path with images.bin, cameras.bin, points3D.bin
os.makedirs(sfm_path,exist_ok=True)
rec.write(sfm_path)
  for _ in range(50):
      # Step 3: Perform triangulation using the existing camera poses
      triangulation.main(
          reference_model=sfm_path,
          sfm_dir = sfm_path,
          image_dir=Path(output_dir),
          pairs=sfm_pairs,
          features=features_path,
          matches=matches_path,
          verbose = False,
          skip_geometric_verification = True
      )
      # # Load the final reconstruction
      reconstruction = pycolmap.Reconstruction(sfm_path)

      # Define bundle adjustment options
      options = pycolmap.BundleAdjustmentOptions()
      options.refine_focal_length = False  # Do not refine focal length
      options.refine_principal_point = False  # Do not refine principal point
      options.refine_extra_params = False  # Do not refine extra parameters
      options.refine_extrinsics = True  # Refine extrinsics
      options.use_gpu = True
      pycolmap.bundle_adjustment(reconstruction, options)
      reconstruction.write(sfm_path)