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Correct snavely reprojection error in code and doc.

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The snavely reprojection error is wrong both in the sample code and
in the documentation. It should not multiply by the focal length
before calculating the distortion.

Change-Id: I292af962e634506a7cc57af9ce72b08f81ce3425
This commit is contained in:
Ricardo Martin
2012-09-19 16:46:06 -07:00
parent 1dc544adb0
commit f9a7ce831e
3 changed files with 20 additions and 19 deletions
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docs/bundleadjustment.tex
+7 -6
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@@ -37,9 +37,8 @@ struct SnavelyReprojectionError {
// 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& focal = camera[6];
T xp = - focal * p[0] / p[2];
T yp = - focal * p[1] / p[2];
T xp = - p[0] / p[2];
T yp = - p[1] / p[2];
// Apply second and fourth order radial distortion.
const T& l1 = camera[7];
@@ -48,8 +47,9 @@ struct SnavelyReprojectionError {
T distortion = T(1.0) + r2 * (l1 + l2 * r2);
// Compute final projected point position.
T predicted_x = distortion * xp;
T predicted_y = distortion * yp;
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 - T(observed_x);
@@ -98,4 +98,5 @@ ceres::Solve(options, &problem, &summary);
std::cout << summary.FullReport() << "\n";
\end{minted}
For a more sophisticated bundle adjustment example which demonstrates the use of Ceres' more advanced features including its various linear solvers, robust loss functions and local parameterizations see \texttt{examples/bundle\_adjuster.cc}.
For a more sophisticated bundle adjustment example which demonstrates the use of Ceres' more advanced features including its various linear solvers, robust loss functions and local parameterizations see \texttt{examples/bundle\_adjuster.cc}.
examples/simple_bundle_adjuster.cc
+5 -5
View File
@@ -139,9 +139,8 @@ struct SnavelyReprojectionError {
// 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& focal = camera[6];
T xp = - focal * p[0] / p[2];
T yp = - focal * p[1] / p[2];
T xp = - p[0] / p[2];
T yp = - p[1] / p[2];
// Apply second and fourth order radial distortion.
const T& l1 = camera[7];
@@ -150,8 +149,9 @@ struct SnavelyReprojectionError {
T distortion = T(1.0) + r2 * (l1 + l2 * r2);
// Compute final projected point position.
T predicted_x = distortion * xp;
T predicted_y = distortion * yp;
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 - T(observed_x);
examples/snavely_reprojection_error.h
+8 -8
View File
@@ -71,8 +71,8 @@ struct SnavelyReprojectionError {
// the camera model that Noah Snavely's Bundler assumes, whereby
// the camera coordinate system has a negative z axis.
const T& focal = camera[6];
T xp = - focal * p[0] / p[2];
T yp = - focal * p[1] / p[2];
T xp = - p[0] / p[2];
T yp = - p[1] / p[2];
// Apply second and fourth order radial distortion.
const T& l1 = camera[7];
@@ -81,8 +81,8 @@ struct SnavelyReprojectionError {
T distortion = T(1.0) + r2 * (l1 + l2 * r2);
// Compute final projected point position.
T predicted_x = distortion * xp;
T predicted_y = distortion * yp;
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 - T(observed_x);
@@ -128,16 +128,16 @@ struct SnavelyReprojectionErrorWithQuaternions {
// 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 = - focal * p[0] / p[2];
T yp = - focal * p[1] / p[2];
T xp = - p[0] / p[2];
T yp = - p[1] / p[2];
// Apply second and fourth order radial distortion.
T r2 = xp*xp + yp*yp;
T distortion = T(1.0) + r2 * (l1 + l2 * r2);
// Compute final projected point position.
T predicted_x = distortion * xp;
T predicted_y = distortion * yp;
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 - T(observed_x);