comment

components/calibration/src/optimize.cpp

@@ -78,6 +78,8 @@ struct ReprojectionError {
 		const T r4 = r2*r2;
 		const T r6 = r4*r2;
 
+		// see also https://github.com/opencv/opencv/blob/b698d0a6ee12342a87b8ad739d908fd8d7ff1fca/modules/calib3d/src/calibration.cpp#L774
+
 		// Radial distortion
 		const T cdist = T(1.0) + k1*r2 + k2*r4 + k3*r6;
 		// Radial distortion: rational model