Method FindLocalBundle

src/colmap/sfm/incremental_mapper_impl.cc:381–552

}

std::vector<image_t> IncrementalMapperImpl::FindLocalBundle(
    const IncrementalMapper::Options& options,
    image_t image_id,
    const Reconstruction& reconstruction) {
  THROW_CHECK(options.Check());

  const Image& image = reconstruction.Image(image_id);
  THROW_CHECK(image.HasPose());

  // Extract all images that have at least one 3D point with the query image
  // in common, and simultaneously count the number of common 3D points.

  std::unordered_map<image_t, size_t> shared_observations;

  std::unordered_set<point3D_t> point3D_ids;
  point3D_ids.reserve(image.NumPoints3D());

  for (const Point2D& point2D : image.Points2D()) {
    if (point2D.HasPoint3D()) {
      point3D_ids.insert(point2D.point3D_id);
      const Point3D& point3D = reconstruction.Point3D(point2D.point3D_id);
      for (const TrackElement& track_el : point3D.track.Elements()) {
        if (track_el.image_id != image_id) {
          shared_observations[track_el.image_id] += 1;
        }
      }
    }
  }

  // Sort overlapping images according to number of shared observations.

  std::vector<std::pair<image_t, size_t>> overlapping_images(
      shared_observations.begin(), shared_observations.end());
  std::sort(overlapping_images.begin(),
            overlapping_images.end(),
            [](const std::pair<image_t, size_t>& image1,
               const std::pair<image_t, size_t>& image2) {
              return image1.second > image2.second;
            });

  // The local bundle is composed of the given image and its most connected
  // neighbor images, hence the subtraction of 1.

  const size_t num_images =
      static_cast<size_t>(options.ba_local_num_images - 1);
  const size_t num_eff_images = std::min(num_images, overlapping_images.size());

  // Extract most connected images and ensure sufficient triangulation angle.

  std::vector<image_t> local_bundle_image_ids;
  local_bundle_image_ids.reserve(num_eff_images);

  // If the number of overlapping images equals the number of desired images
  // in the local bundle, then simply copy over the image identifiers.
  if (overlapping_images.size() == num_eff_images) {
    for (const auto& overlapping_image : overlapping_images) {
      local_bundle_image_ids.push_back(overlapping_image.first);
    }