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diff --git a/examples/simple_bundle_adjuster.cc b/examples/simple_bundle_adjuster.cc
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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2015 Google Inc. All rights reserved.
+// http://ceres-solver.org/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice,
+// this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+// this list of conditions and the following disclaimer in the documentation
+// and/or other materials provided with the distribution.
+// * Neither the name of Google Inc. nor the names of its contributors may be
+// used to endorse or promote products derived from this software without
+// specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: keir@google.com (Keir Mierle)
+//
+// A minimal, self-contained bundle adjuster using Ceres, that reads
+// files from University of Washington' Bundle Adjustment in the Large dataset:
+// http://grail.cs.washington.edu/projects/bal
+//
+// This does not use the best configuration for solving; see the more involved
+// bundle_adjuster.cc file for details.
+
+#include <cmath>
+#include <cstdio>
+#include <iostream>
+
+#include "ceres/ceres.h"
+#include "ceres/rotation.h"
+
+// Read a Bundle Adjustment in the Large dataset.
+class BALProblem {
+ public:
+ ~BALProblem() {
+ delete[] point_index_;
+ delete[] camera_index_;
+ delete[] observations_;
+ delete[] parameters_;
+ }
+
+ int num_observations() const { return num_observations_; }
+ const double* observations() const { return observations_; }
+ double* mutable_cameras() { return parameters_; }
+ double* mutable_points() { return parameters_ + 9 * num_cameras_; }
+
+ double* mutable_camera_for_observation(int i) {
+ return mutable_cameras() + camera_index_[i] * 9;
+ }
+ double* mutable_point_for_observation(int i) {
+ return mutable_points() + point_index_[i] * 3;
+ }
+
+ bool LoadFile(const char* filename) {
+ FILE* fptr = fopen(filename, "r");
+ if (fptr == NULL) {
+ return false;
+ };
+
+ FscanfOrDie(fptr, "%d", &num_cameras_);
+ FscanfOrDie(fptr, "%d", &num_points_);
+ FscanfOrDie(fptr, "%d", &num_observations_);
+
+ point_index_ = new int[num_observations_];
+ camera_index_ = new int[num_observations_];
+ observations_ = new double[2 * num_observations_];
+
+ num_parameters_ = 9 * num_cameras_ + 3 * num_points_;
+ parameters_ = new double[num_parameters_];
+
+ for (int i = 0; i < num_observations_; ++i) {
+ FscanfOrDie(fptr, "%d", camera_index_ + i);
+ FscanfOrDie(fptr, "%d", point_index_ + i);
+ for (int j = 0; j < 2; ++j) {
+ FscanfOrDie(fptr, "%lf", observations_ + 2*i + j);
+ }
+ }
+
+ for (int i = 0; i < num_parameters_; ++i) {
+ FscanfOrDie(fptr, "%lf", parameters_ + i);
+ }
+ return true;
+ }
+
+ private:
+ template<typename T>
+ void FscanfOrDie(FILE *fptr, const char *format, T *value) {
+ int num_scanned = fscanf(fptr, format, value);
+ if (num_scanned != 1) {
+ LOG(FATAL) << "Invalid UW data file.";
+ }
+ }
+
+ int num_cameras_;
+ int num_points_;
+ int num_observations_;
+ int num_parameters_;
+
+ int* point_index_;
+ int* camera_index_;
+ double* observations_;
+ double* parameters_;
+};
+
+// Templated pinhole camera model for used with Ceres. The camera is
+// parameterized using 9 parameters: 3 for rotation, 3 for translation, 1 for
+// focal length and 2 for radial distortion. The principal point is not modeled
+// (i.e. it is assumed be located at the image center).
+struct SnavelyReprojectionError {
+ SnavelyReprojectionError(double observed_x, double observed_y)
+ : observed_x(observed_x), observed_y(observed_y) {}
+
+ template <typename T>
+ bool operator()(const T* const camera,
+ const T* const point,
+ T* residuals) const {
+ // camera[0,1,2] are the angle-axis rotation.
+ T p[3];
+ ceres::AngleAxisRotatePoint(camera, point, p);
+
+ // camera[3,4,5] are the translation.
+ p[0] += camera[3];
+ p[1] += camera[4];
+ p[2] += camera[5];
+
+ // Compute the center of distortion. The sign change comes from
+ // the camera model that Noah Snavely's Bundler assumes, whereby
+ // the camera coordinate system has a negative z axis.
+ T xp = - p[0] / p[2];
+ T yp = - p[1] / p[2];
+
+ // Apply second and fourth order radial distortion.
+ const T& l1 = camera[7];
+ const T& l2 = camera[8];
+ T r2 = xp*xp + yp*yp;
+ T distortion = 1.0 + r2 * (l1 + l2 * r2);
+
+ // Compute final projected point position.
+ const T& focal = camera[6];
+ T predicted_x = focal * distortion * xp;
+ T predicted_y = focal * distortion * yp;
+
+ // The error is the difference between the predicted and observed position.
+ residuals[0] = predicted_x - observed_x;
+ residuals[1] = predicted_y - observed_y;
+
+ return true;
+ }
+
+ // Factory to hide the construction of the CostFunction object from
+ // the client code.
+ static ceres::CostFunction* Create(const double observed_x,
+ const double observed_y) {
+ return (new ceres::AutoDiffCostFunction<SnavelyReprojectionError, 2, 9, 3>(
+ new SnavelyReprojectionError(observed_x, observed_y)));
+ }
+
+ double observed_x;
+ double observed_y;
+};
+
+int main(int argc, char** argv) {
+ google::InitGoogleLogging(argv[0]);
+ if (argc != 2) {
+ std::cerr << "usage: simple_bundle_adjuster <bal_problem>\n";
+ return 1;
+ }
+
+ BALProblem bal_problem;
+ if (!bal_problem.LoadFile(argv[1])) {
+ std::cerr << "ERROR: unable to open file " << argv[1] << "\n";
+ return 1;
+ }
+
+ const double* observations = bal_problem.observations();
+
+ // Create residuals for each observation in the bundle adjustment problem. The
+ // parameters for cameras and points are added automatically.
+ ceres::Problem problem;
+ for (int i = 0; i < bal_problem.num_observations(); ++i) {
+ // Each Residual block takes a point and a camera as input and outputs a 2
+ // dimensional residual. Internally, the cost function stores the observed
+ // image location and compares the reprojection against the observation.
+
+ ceres::CostFunction* cost_function =
+ SnavelyReprojectionError::Create(observations[2 * i + 0],
+ observations[2 * i + 1]);
+ problem.AddResidualBlock(cost_function,
+ NULL /* squared loss */,
+ bal_problem.mutable_camera_for_observation(i),
+ bal_problem.mutable_point_for_observation(i));
+ }
+
+ // Make Ceres automatically detect the bundle structure. Note that the
+ // standard solver, SPARSE_NORMAL_CHOLESKY, also works fine but it is slower
+ // for standard bundle adjustment problems.
+ ceres::Solver::Options options;
+ options.linear_solver_type = ceres::DENSE_SCHUR;
+ options.minimizer_progress_to_stdout = true;
+
+ ceres::Solver::Summary summary;
+ ceres::Solve(options, &problem, &summary);
+ std::cout << summary.FullReport() << "\n";
+ return 0;
+}