aout rajkataria / ReliableResectioning MDS initializing

[coder12333444]

@lxxue
Hi,sorry to bother you. when mds initializing, is the database a new database or is it generated after image extracting and image matching?

[lxxue]

Hi, the author creates a new database (also overwrites the old one as they have the same name) and go over the correspondences as shown here:

sfm-disambiguation-colmap/reliable_resectioning/src/base/mds.cc

Lines 40 to 98 in b78896b

	Database database(database_path_ + "/database.db");
	images = database.ReadAllImages();
	for (std::vector<Image>::iterator it = images.begin(); it != images.end();
	++it) {
	image_names.push_back(it->Name());
	}
	std::sort(image_names.begin(), image_names.end());
	CorrespondenceGraph sg = database_cache->CorrespondenceGraph();
	for (auto const &im1 : image_names) {
	std::map<std::string, float> im1_aam_map;
	for (auto const &im2 : image_names) {
	if (im1.compare(im2) == 0) {
	im1_aam_map.insert(std::make_pair(im2, 0.0));
	} else if (im1.compare(im2) > 0) {
	im1_aam_map.insert(std::make_pair(
	im2, aam_distances_map.find(im2)->second.find(im1)->second));
	} else {
	Image im1_ = database.ReadImageWithName(im1);
	Image im2_ = database.ReadImageWithName(im2);
	if (!sg.ExistsImage(im1_.ImageId()) ||
	!sg.ExistsImage(im2_.ImageId())) {
	continue;
	}
	colmap::FeatureMatches correspondences =
	sg.FindCorrespondencesBetweenImages(im1_.ImageId(), im2_.ImageId());
	colmap::FeatureMatches::iterator correspondence_itr;
	double aam_matches = 0.0;
	for (correspondence_itr = correspondences.begin();
	correspondence_itr != correspondences.end();
	++correspondence_itr) {
	std::vector<CorrespondenceGraph::Correspondence>
	point_correspondences = sg.FindCorrespondences(
	im1_.ImageId(), (*correspondence_itr).point2D_idx1);
	if (!sg.HasCorrespondences(im1_.ImageId(),
	(*correspondence_itr).point2D_idx1)) {
	continue;
	}
	if (!sg.HasCorrespondences(im2_.ImageId(),
	(*correspondence_itr).point2D_idx2)) {
	continue;
	}
	// tuned parameters
	// aam_matches += pow(0.5, point_correspondences.size() - 1);
	aam_matches += pow(0.3, point_correspondences.size() - 1);
	}
	im1_aam_map.insert(std::make_pair(im2, 1.0 / (aam_matches + 0.000001)));
	}
	}
	aam_distances_map.insert(std::make_pair(im1, im1_aam_map));
	}
	std::cout
	<< "******************************************************** Finished "
	"Initializing MDS ************************************************"
	<< std::endl;
	}

I think the matches are in the DatabaseCache and not computed from scratch again.

[coder12333444]

@lxxue
Hi,
if creates a new database,the " images = database.ReadAllImages(); " images.size ==0,then image_names.size ==0;the for (auto const &im1 : image_names) do not exec ,so I think the database.db is the result of image extracting and image matching,do you think?

[lxxue]

Sorry for the wrong answer: "the author creates a new database (also overwrites the old one".

Yes, you are right the author didn't create a new database. They just use the matches from database.db.