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// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2010, 2011, 2012 Google Inc. All rights reserved.
// http://code.google.com/p/ceres-solver/
//
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// modification, are permitted provided that the following conditions are met:
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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 <string>
#include <vector>
#include <gflags/gflags.h>
#include <glog/logging.h>
#include "bal_problem.h"
#include "snavely_reprojection_error.h"
#include "ceres/ceres.h"
DEFINE_string(input, "", "Input File name");
DEFINE_string(solver_type, "sparse_schur", "Options are: "
"sparse_schur, dense_schur, iterative_schur, cholesky "
"and dense_qr");
DEFINE_string(preconditioner_type, "jacobi", "Options are: "
"identity, jacobi, schur_jacobi, cluster_jacobi, "
"cluster_tridiagonal");
DEFINE_int32(num_iterations, 5, "Number of iterations");
DEFINE_int32(num_threads, 1, "Number of threads");
DEFINE_bool(use_schur_ordering, false, "Use automatic Schur ordering.");
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");
namespace ceres {
namespace examples {
void SetLinearSolver(Solver::Options* options) {
if (FLAGS_solver_type == "sparse_schur") {
options->linear_solver_type = ceres::SPARSE_SCHUR;
} else if (FLAGS_solver_type == "dense_schur") {
options->linear_solver_type = ceres::DENSE_SCHUR;
} else if (FLAGS_solver_type == "iterative_schur") {
options->linear_solver_type = ceres::ITERATIVE_SCHUR;
} else if (FLAGS_solver_type == "cholesky") {
options->linear_solver_type = ceres::SPARSE_NORMAL_CHOLESKY;
} else if (FLAGS_solver_type == "dense_qr") {
// DENSE_QR is included here for completeness, but actually using
// this opttion is a bad idea due to the amount of memory needed
// to store even the smallest of the bundle adjustment jacobian
// arrays
options->linear_solver_type = ceres::DENSE_QR;
} else {
LOG(FATAL) << "Unknown ceres solver type: "
<< FLAGS_solver_type;
}
if (options->linear_solver_type == ceres::ITERATIVE_SCHUR) {
options->linear_solver_min_num_iterations = 5;
if (FLAGS_preconditioner_type == "identity") {
options->preconditioner_type = ceres::IDENTITY;
} else if (FLAGS_preconditioner_type == "jacobi") {
options->preconditioner_type = ceres::JACOBI;
} else if (FLAGS_preconditioner_type == "schur_jacobi") {
options->preconditioner_type = ceres::SCHUR_JACOBI;
} else if (FLAGS_preconditioner_type == "cluster_jacobi") {
options->preconditioner_type = ceres::CLUSTER_JACOBI;
} else if (FLAGS_preconditioner_type == "cluster_tridiagonal") {
options->preconditioner_type = ceres::CLUSTER_TRIDIAGONAL;
} else {
LOG(FATAL) << "Unknown ceres preconditioner type: "
<< FLAGS_preconditioner_type;
}
}
options->num_linear_solver_threads = FLAGS_num_threads;
}
void SetOrdering(BALProblem* bal_problem, Solver::Options* options) {
// 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. Using them however requires that the ParameterBlocks
// are in a particular order (points before cameras) and
// Solver::Options::num_eliminate_blocks is set to the number of
// points.
//
// 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_use_schur_ordering) {
options->ordering_type = ceres::SCHUR;
return;
}
options->ordering_type = ceres::USER;
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();
// The points come before the cameras.
for (int i = 0; i < num_points; ++i) {
options->ordering.push_back(points + point_block_size * i);
}
for (int i = 0; i < num_cameras; ++i) {
// When using axis-angle, there is a single parameter block for
// the entire camera.
options->ordering.push_back(cameras + camera_block_size * i);
// If quaternions are used, there are two blocks, so add the
// second block to the ordering.
if (FLAGS_use_quaternions) {
options->ordering.push_back(cameras + camera_block_size * i + 4);
}
}
options->num_eliminate_blocks = num_points;
}
void SetMinimizerOptions(Solver::Options* options) {
options->max_num_iterations = FLAGS_num_iterations;
options->minimizer_progress_to_stdout = true;
options->num_threads = FLAGS_num_threads;
}
void SetSolverOptionsFromFlags(BALProblem* bal_problem,
Solver::Options* options) {
SetLinearSolver(options);
SetOrdering(bal_problem, options);
SetMinimizerOptions(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.
if (FLAGS_use_quaternions) {
cost_function = new AutoDiffCostFunction<
SnavelyReprojectionErrorWitQuaternions, 2, 4, 6, 3>(
new SnavelyReprojectionErrorWitQuaternions(
observations[2 * i + 0],
observations[2 * i + 1]));
} else {
cost_function =
new AutoDiffCostFunction<SnavelyReprojectionError, 2, 9, 3>(
new SnavelyReprojectionError(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];
if (FLAGS_use_quaternions) {
// When using quaternions, we split the camera into two
// parameter blocks. One of size 4 for the quaternion and the
// other of size 6 containing the translation, focal length and
// the radial distortion parameters.
problem->AddResidualBlock(cost_function,
loss_function,
camera,
camera + 4,
point);
} else {
problem->AddResidualBlock(cost_function, loss_function, camera, point);
}
}
if (FLAGS_use_quaternions && FLAGS_use_local_parameterization) {
LocalParameterization* quaternion_parameterization =
new QuaternionParameterization;
for (int i = 0; i < bal_problem->num_cameras(); ++i) {
problem->SetParameterization(cameras + camera_block_size * i,
quaternion_parameterization);
}
}
}
void SolveProblem(const char* filename) {
BALProblem bal_problem(filename, FLAGS_use_quaternions);
Problem problem;
BuildProblem(&bal_problem, &problem);
Solver::Options options;
SetSolverOptionsFromFlags(&bal_problem, &options);
Solver::Summary summary;
Solve(options, &problem, &summary);
std::cout << summary.FullReport() << "\n";
}
} // namespace examples
} // namespace ceres
int main(int argc, char** argv) {
google::ParseCommandLineFlags(&argc, &argv, true);
google::InitGoogleLogging(argv[0]);
if (FLAGS_input.empty()) {
LOG(ERROR) << "Usage: bundle_adjustment_example --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;
}