ceres-solver/internal/ceres/autodiff_benchmarks/snavely_reprojection_error.h

// Ceres Solver - A fast non-linear least squares minimizer
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// Author: darius.rueckert@fau.de (Darius Rueckert)
//
//
#ifndef CERES_INTERNAL_AUTODIFF_BENCHMARK_SNAVELY_REPROJECTION_ERROR_H_
#define CERES_INTERNAL_AUTODIFF_BENCHMARK_SNAVELY_REPROJECTION_ERROR_H_

#include "ceres/rotation.h"

namespace ceres {

struct SnavelyReprojectionError {
  SnavelyReprojectionError(double observed_x, double observed_y)
      : observed_x(observed_x), observed_y(observed_y) {}

  SnavelyReprojectionError() = default;
  template <typename T>
  inline bool operator()(const T* const camera,
                         const T* const point,
                         T* residuals) const {
    T ox = T(observed_x);
    T oy = T(observed_y);

    // 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.
    const T xp = -p[0] / p[2];
    const T yp = -p[1] / p[2];

    // Apply second and fourth order radial distortion.
    const T& l1 = camera[7];
    const T& l2 = camera[8];
    const T r2 = xp * xp + yp * yp;
    const T distortion = T(1.0) + r2 * (l1 + l2 * r2);

    // Compute final projected point position.
    const T& focal = camera[6];
    const T predicted_x = focal * distortion * xp;
    const T predicted_y = focal * distortion * yp;

    // The error is the difference between the predicted and observed position.
    residuals[0] = predicted_x - ox;
    residuals[1] = predicted_y - oy;

    return true;
  }
  double observed_x;
  double observed_y;
};
}  // namespace ceres
#endif  // CERES_INTERNAL_AUTODIFF_BENCHMARK_SNAVELY_REPROJECTION_ERROR_H_