// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2015 Google Inc. All rights reserved.
// http://ceres-solver.org/
//
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//
// Author: sameeragarwal@google.com (Sameer Agarwal)
//
// An example of solving a dynamically sized problem with various
// solvers and loss functions.
//
// For a simpler bare bones example of doing bundle adjustment with
// Ceres, please see simple_bundle_adjuster.cc.
//
// NOTE: This example will not compile without gflags and SuiteSparse.
//
// The problem being solved here is known as a Bundle Adjustment
// problem in computer vision. Given a set of 3d points X_1, ..., X_n,
// a set of cameras P_1, ..., P_m. If the point X_i is visible in
// image j, then there is a 2D observation u_ij that is the expected
// projection of X_i using P_j. The aim of this optimization is to
// find values of X_i and P_j such that the reprojection error
//
// E(X,P) = sum_ij |u_ij - P_j X_i|^2
//
// is minimized.
//
// The problem used here comes from a collection of bundle adjustment
// problems published at University of Washington.
// http://grail.cs.washington.edu/projects/bal
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <vector>
#include "bal_problem.h"
#include "ceres/ceres.h"
#include "gflags/gflags.h"
#include "glog/logging.h"
#include "snavely_reprojection_error.h"
DEFINE_string(input, "", "Input File name");
DEFINE_string(trust_region_strategy, "levenberg_marquardt",
"Options are: levenberg_marquardt, dogleg.");
DEFINE_string(dogleg, "traditional_dogleg", "Options are: traditional_dogleg,"
"subspace_dogleg.");
DEFINE_bool(inner_iterations, false, "Use inner iterations to non-linearly "
"refine each successful trust region step.");
DEFINE_string(blocks_for_inner_iterations, "automatic", "Options are: "
"automatic, cameras, points, cameras,points, points,cameras");
DEFINE_string(linear_solver, "sparse_schur", "Options are: "
"sparse_schur, dense_schur, iterative_schur, sparse_normal_cholesky, "
"dense_qr, dense_normal_cholesky and cgnr.");
DEFINE_bool(explicit_schur_complement, false, "If using ITERATIVE_SCHUR "
"then explicitly compute the Schur complement.");
DEFINE_string(preconditioner, "jacobi", "Options are: "
"identity, jacobi, schur_jacobi, cluster_jacobi, "
"cluster_tridiagonal.");
DEFINE_string(visibility_clustering, "canonical_views",
"single_linkage, canonical_views");
DEFINE_string(sparse_linear_algebra_library, "suite_sparse",
"Options are: suite_sparse and cx_sparse.");
DEFINE_string(dense_linear_algebra_library, "eigen",
"Options are: eigen and lapack.");
DEFINE_string(ordering, "automatic", "Options are: automatic, user.");
DEFINE_bool(use_quaternions, false, "If true, uses quaternions to represent "
"rotations. If false, angle axis is used.");
DEFINE_bool(use_local_parameterization, false, "For quaternions, use a local "
"parameterization.");
DEFINE_bool(robustify, false, "Use a robust loss function.");
DEFINE_double(eta, 1e-2, "Default value for eta. Eta determines the "
"accuracy of each linear solve of the truncated newton step. "
"Changing this parameter can affect solve performance.");
DEFINE_int32(num_threads, 1, "Number of threads.");
DEFINE_int32(num_iterations, 5, "Number of iterations.");
DEFINE_double(max_solver_time, 1e32, "Maximum solve time in seconds.");
DEFINE_bool(nonmonotonic_steps, false, "Trust region algorithm can use"
" nonmonotic steps.");
DEFINE_double(rotation_sigma, 0.0, "Standard deviation of camera rotation "
"perturbation.");
DEFINE_double(translation_sigma, 0.0, "Standard deviation of the camera "
"translation perturbation.");
DEFINE_double(point_sigma, 0.0, "Standard deviation of the point "
"perturbation.");
DEFINE_int32(random_seed, 38401, "Random seed used to set the state "
"of the pseudo random number generator used to generate "
"the pertubations.");
DEFINE_bool(line_search, false, "Use a line search instead of trust region "
"algorithm.");
DEFINE_string(initial_ply, "", "Export the BAL file data as a PLY file.");
DEFINE_string(final_ply, "", "Export the refined BAL file data as a PLY "
"file.");
namespace ceres {
namespace examples {
void SetLinearSolver(Solver::Options* options) {
CHECK(StringToLinearSolverType(FLAGS_linear_solver,
&options->linear_solver_type));
CHECK(StringToPreconditionerType(FLAGS_preconditioner,
&options->preconditioner_type));
CHECK(StringToVisibilityClusteringType(FLAGS_visibility_clustering,
&options->visibility_clustering_type));
CHECK(StringToSparseLinearAlgebraLibraryType(
FLAGS_sparse_linear_algebra_library,
&options->sparse_linear_algebra_library_type));
CHECK(StringToDenseLinearAlgebraLibraryType(
FLAGS_dense_linear_algebra_library,
&options->dense_linear_algebra_library_type));
options->num_linear_solver_threads = FLAGS_num_threads;
options->use_explicit_schur_complement = FLAGS_explicit_schur_complement;
}
void SetOrdering(BALProblem* bal_problem, Solver::Options* options) {
const int num_points = bal_problem->num_points();
const int point_block_size = bal_problem->point_block_size();
double* points = bal_problem->mutable_points();
const int num_cameras = bal_problem->num_cameras();
const int camera_block_size = bal_problem->camera_block_size();
double* cameras = bal_problem->mutable_cameras();
if (options->use_inner_iterations) {
if (FLAGS_blocks_for_inner_iterations == "cameras") {
LOG(INFO) << "Camera blocks for inner iterations";
options->inner_iteration_ordering.reset(new ParameterBlockOrdering);
for (int i = 0; i < num_cameras; ++i) {
options->inner_iteration_ordering->AddElementToGroup(cameras + camera_block_size * i, 0);
}
} else if (FLAGS_blocks_for_inner_iterations == "points") {
LOG(INFO) << "Point blocks for inner iterations";
options->inner_iteration_ordering.reset(new ParameterBlockOrdering);
for (int i = 0; i < num_points; ++i) {
options->inner_iteration_ordering->AddElementToGroup(points + point_block_size * i, 0);
}
} else if (FLAGS_blocks_for_inner_iterations == "cameras,points") {
LOG(INFO) << "Camera followed by point blocks for inner iterations";
options->inner_iteration_ordering.reset(new ParameterBlockOrdering);
for (int i = 0; i < num_cameras; ++i) {
options->inner_iteration_ordering->AddElementToGroup(cameras + camera_block_size * i, 0);
}
for (int i = 0; i < num_points; ++i) {
options->inner_iteration_ordering->AddElementToGroup(points + point_block_size * i, 1);
}
} else if (FLAGS_blocks_for_inner_iterations == "points,cameras") {
LOG(INFO) << "Point followed by camera blocks for inner iterations";
options->inner_iteration_ordering.reset(new ParameterBlockOrdering);
for (int i = 0; i < num_cameras; ++i) {
options->inner_iteration_ordering->AddElementToGroup(cameras + camera_block_size * i, 1);
}
for (int i = 0; i < num_points; ++i) {
options->inner_iteration_ordering->AddElementToGroup(points + point_block_size * i, 0);
}
} else if (FLAGS_blocks_for_inner_iterations == "automatic") {
LOG(INFO) << "Choosing automatic blocks for inner iterations";
} else {
LOG(FATAL) << "Unknown block type for inner iterations: "
<< FLAGS_blocks_for_inner_iterations;
}
}
// Bundle adjustment problems have a sparsity structure that makes
// them amenable to more specialized and much more efficient
// solution strategies. The SPARSE_SCHUR, DENSE_SCHUR and
// ITERATIVE_SCHUR solvers make use of this specialized
// structure.
//
// This can either be done by specifying Options::ordering_type =
// ceres::SCHUR, in which case Ceres will automatically determine
// the right ParameterBlock ordering, or by manually specifying a
// suitable ordering vector and defining
// Options::num_eliminate_blocks.
if (FLAGS_ordering == "automatic") {
return;
}
ceres::ParameterBlockOrdering* ordering =
new ceres::ParameterBlockOrdering;
// The points come before the cameras.
for (int i = 0; i < num_points; ++i) {
ordering->AddElementToGroup(points + point_block_size * i, 0);
}
for (int i = 0; i < num_cameras; ++i) {
// When using axis-angle, there is a single parameter block for
// the entire camera.
ordering->AddElementToGroup(cameras + camera_block_size * i, 1);
}
options->linear_solver_ordering.reset(ordering);
}
void SetMinimizerOptions(Solver::Options* options) {
options->max_num_iterations = FLAGS_num_iterations;
options->minimizer_progress_to_stdout = true;
options->num_threads = FLAGS_num_threads;
options->eta = FLAGS_eta;
options->max_solver_time_in_seconds = FLAGS_max_solver_time;
options->use_nonmonotonic_steps = FLAGS_nonmonotonic_steps;
if (FLAGS_line_search) {
options->minimizer_type = ceres::LINE_SEARCH;
}
CHECK(StringToTrustRegionStrategyType(FLAGS_trust_region_strategy,
&options->trust_region_strategy_type));
CHECK(StringToDoglegType(FLAGS_dogleg, &options->dogleg_type));
options->use_inner_iterations = FLAGS_inner_iterations;
}
void SetSolverOptionsFromFlags(BALProblem* bal_problem,
Solver::Options* options) {
SetMinimizerOptions(options);
SetLinearSolver(options);
SetOrdering(bal_problem, options);
}
void BuildProblem(BALProblem* bal_problem, Problem* problem) {
const int point_block_size = bal_problem->point_block_size();
const int camera_block_size = bal_problem->camera_block_size();
double* points = bal_problem->mutable_points();
double* cameras = bal_problem->mutable_cameras();
// Observations is 2*num_observations long array observations =
// [u_1, u_2, ... , u_n], where each u_i is two dimensional, the x
// and y positions of the observation.
const double* observations = bal_problem->observations();
for (int i = 0; i < bal_problem->num_observations(); ++i) {
CostFunction* cost_function;
// Each Residual block takes a point and a camera as input and
// outputs a 2 dimensional residual.
cost_function =
(FLAGS_use_quaternions)
? SnavelyReprojectionErrorWithQuaternions::Create(
observations[2 * i + 0],
observations[2 * i + 1])
: SnavelyReprojectionError::Create(
observations[2 * i + 0],
observations[2 * i + 1]);
// If enabled use Huber's loss function.
LossFunction* loss_function = FLAGS_robustify ? new HuberLoss(1.0) : NULL;
// Each observation correponds to a pair of a camera and a point
// which are identified by camera_index()[i] and point_index()[i]
// respectively.
double* camera =
cameras + camera_block_size * bal_problem->camera_index()[i];
double* point = points + point_block_size * bal_problem->point_index()[i];
problem->AddResidualBlock(cost_function, loss_function, camera, point);
}
if (FLAGS_use_quaternions && FLAGS_use_local_parameterization) {
LocalParameterization* camera_parameterization =
new ProductParameterization(
new QuaternionParameterization(),
new IdentityParameterization(6));
for (int i = 0; i < bal_problem->num_cameras(); ++i) {
problem->SetParameterization(cameras + camera_block_size * i,
camera_parameterization);
}
}
}
void SolveProblem(const char* filename) {
BALProblem bal_problem(filename, FLAGS_use_quaternions);
if (!FLAGS_initial_ply.empty()) {
bal_problem.WriteToPLYFile(FLAGS_initial_ply);
}
Problem problem;
srand(FLAGS_random_seed);
bal_problem.Normalize();
bal_problem.Perturb(FLAGS_rotation_sigma,
FLAGS_translation_sigma,
FLAGS_point_sigma);
BuildProblem(&bal_problem, &problem);
Solver::Options options;
SetSolverOptionsFromFlags(&bal_problem, &options);
options.gradient_tolerance = 1e-16;
options.function_tolerance = 1e-16;
Solver::Summary summary;
Solve(options, &problem, &summary);
std::cout << summary.FullReport() << "\n";
if (!FLAGS_final_ply.empty()) {
bal_problem.WriteToPLYFile(FLAGS_final_ply);
}
}
} // namespace examples
} // namespace ceres
int main(int argc, char** argv) {
CERES_GFLAGS_NAMESPACE::ParseCommandLineFlags(&argc, &argv, true);
google::InitGoogleLogging(argv[0]);
if (FLAGS_input.empty()) {
LOG(ERROR) << "Usage: bundle_adjuster --input=bal_problem";
return 1;
}
CHECK(FLAGS_use_quaternions || !FLAGS_use_local_parameterization)
<< "--use_local_parameterization can only be used with "
<< "--use_quaternions.";
ceres::examples::SolveProblem(FLAGS_input.c_str());
return 0;
}