Add camera intrinsics priors and parameter bounds to bundle adjustment

src/colmap/controllers/incremental_pipeline.cc

@@ -176,6 +176,13 @@ BundleAdjustmentOptions IncrementalPipelineOptions::LocalBundleAdjustment()
   options.refine_principal_point = ba_refine_principal_point;
   options.refine_extra_params = ba_refine_extra_params;
   options.refine_sensor_from_rig = ba_refine_sensor_from_rig;
+  options.focal_length_prior_weight = ba_focal_length_prior_weight;
+  options.principal_point_prior_weight = ba_principal_point_prior_weight;
+  options.extra_params_prior_weight = ba_extra_params_prior_weight;
+  options.bound_camera_params = ba_bound_camera_params;
+  options.min_focal_length_ratio = min_focal_length_ratio;
+  options.max_focal_length_ratio = max_focal_length_ratio;
+  options.max_extra_param = max_extra_param;
   if (options.ceres) {
     options.ceres->solver_options.function_tolerance =
         ba_local_function_tolerance;
@@ -219,6 +226,13 @@ BundleAdjustmentOptions IncrementalPipelineOptions::GlobalBundleAdjustment()
   options.refine_principal_point = ba_refine_principal_point;
   options.refine_extra_params = ba_refine_extra_params;
   options.refine_sensor_from_rig = ba_refine_sensor_from_rig;
+  options.focal_length_prior_weight = ba_focal_length_prior_weight;
+  options.principal_point_prior_weight = ba_principal_point_prior_weight;
+  options.extra_params_prior_weight = ba_extra_params_prior_weight;
+  options.bound_camera_params = ba_bound_camera_params;
+  options.min_focal_length_ratio = min_focal_length_ratio;
+  options.max_focal_length_ratio = max_focal_length_ratio;
+  options.max_extra_param = max_extra_param;
   if (options.ceres) {
     options.ceres->solver_options.function_tolerance =
         ba_global_function_tolerance;
@@ -286,6 +300,9 @@ bool IncrementalPipelineOptions::Check() const {
   CHECK_OPTION_GT(min_focal_length_ratio, 0);
   CHECK_OPTION_GT(max_focal_length_ratio, 0);
   CHECK_OPTION_GE(max_extra_param, 0);
+  CHECK_OPTION_GE(ba_focal_length_prior_weight, 0);
+  CHECK_OPTION_GE(ba_principal_point_prior_weight, 0);
+  CHECK_OPTION_GE(ba_extra_params_prior_weight, 0);
   CHECK_OPTION_GE(ba_local_max_num_iterations, -1);
   CHECK_OPTION_GT(ba_global_frames_ratio, 1.0);
   CHECK_OPTION_GT(ba_global_points_ratio, 1.0);

src/colmap/controllers/incremental_pipeline.h

@@ -77,6 +77,18 @@ struct IncrementalPipelineOptions {
   bool ba_refine_principal_point = false;
   bool ba_refine_extra_params = true;
 
+  // Weights for soft priors on the camera intrinsics during bundle
+  // adjustment. A weight of 0 disables the respective prior. See
+  // BundleAdjustmentOptions for details.
+  double ba_focal_length_prior_weight = 0;
+  double ba_principal_point_prior_weight = 0;
+  double ba_extra_params_prior_weight = 0;
+
+  // Whether to constrain the camera intrinsics during bundle adjustment to
+  // the same bounds that the degenerate intrinsics filter above applies. See
+  // BundleAdjustmentOptions::bound_camera_params.
+  bool ba_bound_camera_params = false;
+
   // Whether to optimize rig poses during the reconstruction.
   bool ba_refine_sensor_from_rig = true;
 

src/colmap/controllers/option_manager.cc

@@ -577,6 +577,20 @@ void OptionManager::AddBundleAdjustmentOptions() {
                    &bundle_adjustment->constant_rig_from_world_rotation);
   AddDefaultOption("BundleAdjustment.min_track_length",
                    &bundle_adjustment->min_track_length);
+  AddDefaultOption("BundleAdjustment.focal_length_prior_weight",
+                   &bundle_adjustment->focal_length_prior_weight);
+  AddDefaultOption("BundleAdjustment.principal_point_prior_weight",
+                   &bundle_adjustment->principal_point_prior_weight);
+  AddDefaultOption("BundleAdjustment.extra_params_prior_weight",
+                   &bundle_adjustment->extra_params_prior_weight);
+  AddDefaultOption("BundleAdjustment.bound_camera_params",
+                   &bundle_adjustment->bound_camera_params);
+  AddDefaultOption("BundleAdjustment.min_focal_length_ratio",
+                   &bundle_adjustment->min_focal_length_ratio);
+  AddDefaultOption("BundleAdjustment.max_focal_length_ratio",
+                   &bundle_adjustment->max_focal_length_ratio);
+  AddDefaultOption("BundleAdjustment.max_extra_param",
+                   &bundle_adjustment->max_extra_param);
   AddDefaultEnumOption("BundleAdjustment.backend",
                        &bundle_adjustment->backend,
                        BundleAdjustmentBackendToString,
@@ -686,6 +700,14 @@ void OptionManager::AddMapperOptions() {
                    &mapper->ba_refine_extra_params);
   AddDefaultOption("Mapper.ba_refine_sensor_from_rig",
                    &mapper->ba_refine_sensor_from_rig);
+  AddDefaultOption("Mapper.ba_focal_length_prior_weight",
+                   &mapper->ba_focal_length_prior_weight);
+  AddDefaultOption("Mapper.ba_principal_point_prior_weight",
+                   &mapper->ba_principal_point_prior_weight);
+  AddDefaultOption("Mapper.ba_extra_params_prior_weight",
+                   &mapper->ba_extra_params_prior_weight);
+  AddDefaultOption("Mapper.ba_bound_camera_params",
+                   &mapper->ba_bound_camera_params);
   AddDefaultOption("Mapper.ba_local_function_tolerance",
                    &mapper->ba_local_function_tolerance);
   AddDefaultOption("Mapper.ba_local_max_num_iterations",
@@ -875,6 +897,26 @@ void OptionManager::AddGlobalMapperOptions() {
                    &global_mapper->mapper.bundle_adjustment.refine_points3D);
   AddDefaultOption("GlobalMapper.ba_min_track_length",
                    &global_mapper->mapper.bundle_adjustment.min_track_length);
+  AddDefaultOption(
+      "GlobalMapper.ba_focal_length_prior_weight",
+      &global_mapper->mapper.bundle_adjustment.focal_length_prior_weight);
+  AddDefaultOption(
+      "GlobalMapper.ba_principal_point_prior_weight",
+      &global_mapper->mapper.bundle_adjustment.principal_point_prior_weight);
+  AddDefaultOption(
+      "GlobalMapper.ba_extra_params_prior_weight",
+      &global_mapper->mapper.bundle_adjustment.extra_params_prior_weight);
+  AddDefaultOption(
+      "GlobalMapper.ba_bound_camera_params",
+      &global_mapper->mapper.bundle_adjustment.bound_camera_params);
+  AddDefaultOption(
+      "GlobalMapper.ba_min_focal_length_ratio",
+      &global_mapper->mapper.bundle_adjustment.min_focal_length_ratio);
+  AddDefaultOption(
+      "GlobalMapper.ba_max_focal_length_ratio",
+      &global_mapper->mapper.bundle_adjustment.max_focal_length_ratio);
+  AddDefaultOption("GlobalMapper.ba_max_extra_param",
+                   &global_mapper->mapper.bundle_adjustment.max_extra_param);
   AddDefaultEnumOption("GlobalMapper.ba_backend",
                        &global_mapper->mapper.bundle_adjustment.backend,
                        BundleAdjustmentBackendToString,

src/colmap/estimators/bundle_adjustment.cc

@@ -5,6 +5,7 @@
 #include "colmap/estimators/bundle_adjustment_caspar.h"
 #include "colmap/estimators/bundle_adjustment_ceres.h"
 #include "colmap/util/hash_containers.h"
+#include "colmap/util/logging.h"
 
 namespace colmap {
 
@@ -281,6 +282,12 @@ BundleAdjustmentBackendOptions& BundleAdjustmentBackendOptions::operator=(
 }
 
 bool BundleAdjustmentOptions::Check() const {
+  CHECK_OPTION_GE(focal_length_prior_weight, 0);
+  CHECK_OPTION_GE(principal_point_prior_weight, 0);
+  CHECK_OPTION_GE(extra_params_prior_weight, 0);
+  CHECK_OPTION_GT(min_focal_length_ratio, 0);
+  CHECK_OPTION_GE(max_focal_length_ratio, min_focal_length_ratio);
+  CHECK_OPTION_GE(max_extra_param, 0);
   return THROW_CHECK_NOTNULL(ceres)->Check();
 }
 
@@ -293,6 +300,15 @@ std::unique_ptr<BundleAdjuster> CreateDefaultBundleAdjuster(
       return CreateDefaultCeresBundleAdjuster(options, config, reconstruction);
     case BundleAdjustmentBackend::CASPAR:
 #ifdef CASPAR_ENABLED
+      if (options.focal_length_prior_weight > 0 ||
+          options.principal_point_prior_weight > 0 ||
+          options.extra_params_prior_weight > 0 ||
+          options.bound_camera_params) {
+        LOG_FIRST_N(WARNING, 1)
+            << "Camera intrinsics priors and parameter bounds are not "
+               "supported by the Caspar bundle adjustment backend and are "
+               "ignored";
+      }
       return CreateDefaultCasparBundleAdjuster(options, config, reconstruction);
 #else
       LOG(FATAL_THROW)

src/colmap/estimators/bundle_adjustment.h

@@ -176,6 +176,44 @@ struct BundleAdjustmentOptions : public BundleAdjustmentBackendOptions {
   // Whether to print a final summary.
   bool print_summary = true;
 
+  // Weights for soft priors on the camera intrinsics. Each weight is the
+  // inverse standard deviation of the assumed Gaussian prior, i.e.
+  // weight = 1 / stddev, so a weight of 0 means an infinite standard deviation
+  // and disables the respective prior.
+  //
+  // The focal length and principal point weights are direct multipliers on
+  // deviations in pixels. The extra parameter weight is multiplied by the mean
+  // focal length at the time the problem is constructed to convert
+  // dimensionless deviations to pixel-like residuals. Note that the effective
+  // strength of the extra parameter prior therefore depends on the field of
+  // view: at equal resolution, a small field-of-view camera is pulled towards
+  // its prior more strongly than a wide field-of-view one.
+  //
+  // The focal length prior is only applied to cameras with
+  // Camera::has_prior_focal_length and pulls towards the focal length at the
+  // time the problem is constructed. Thus "initial" means the construction-time
+  // value for each bundle adjustment problem, not necessarily the original
+  // database value. The prior therefore acts as a damping term across
+  // successive problems rather than as an anchor to the original prior, e.g.
+  // EXIF focal length. The principal point and extra parameter priors pull
+  // towards the values the camera model initializes them to, i.e. the image
+  // center and, for most models, zero.
+  double focal_length_prior_weight = 0;
+  double principal_point_prior_weight = 0;
+  double extra_params_prior_weight = 0;
+
+  // Whether to constrain the camera parameters to bounds that are consistent
+  // with Camera::HasBogusParams, such that the intrinsics cannot leave the
+  // region that the bogus parameter filter considers valid. Parameters that
+  // already violate the bounds are clamped into them.
+  bool bound_camera_params = false;
+
+  // Bounds for the camera parameters, only used if bound_camera_params is set.
+  // The focal length bounds are relative to the maximum image dimension.
+  double min_focal_length_ratio = 0.1;
+  double max_focal_length_ratio = 10.0;
+  double max_extra_param = 1.0;
+
   // Solver backend to use for bundle adjustment.
   BundleAdjustmentBackend backend = BundleAdjustmentBackend::CERES;