filter out bad constraint points

src/aliceVision/sfm/pipeline/expanding/SfmBundle.cpp

@@ -1,4 +1,5 @@
 // This file is part of the AliceVision project.
+// Copyright (c) 2025 AliceVision contributors.
 // Copyright (c) 2024 AliceVision contributors.
 // This Source Code Form is subject to the terms of the Mozilla Public License,
 // v. 2.0. If a copy of the MPL was not distributed with this file,
@@ -54,16 +55,20 @@ bool SfmBundle::cleanup(sfmData::SfMData & sfmData)
     // Remove landmarks without enough observed parallax
     const std::size_t nbOutliersAngleErr = removeOutliersWithAngleError(sfmData, _minAngleForLandmark);
 
+    // Remove constraints which are too far away from landmark
+    const std::size_t nbOutliersConstraints =  removeConstraints(sfmData, _maxConstraintDistance);
+
     // Remove poses without enough observations in an interative fashion
     const std::size_t nbOutliers = nbOutliersResidualErr + nbOutliersAngleErr;
     std::set<IndexT> removedViewsIdIteration;
     bool somethingErased = eraseUnstablePosesAndObservations(sfmData, _minPointsPerPose, _minTrackLength, &removedViewsIdIteration);
 
-    bool somethingChanged = /*somethingErased || */(nbOutliers > _bundleAdjustmentMaxOutlier);
+    bool somethingChanged = /*somethingErased || */(nbOutliers > _bundleAdjustmentMaxOutlier) || (nbOutliersConstraints > 0);
 
     ALICEVISION_LOG_INFO("SfmBundle::cleanup : ");
     ALICEVISION_LOG_INFO(" - nbOutliersResidualErr : " << nbOutliersResidualErr);
     ALICEVISION_LOG_INFO(" - nbOutliersAngleErr : " << nbOutliersAngleErr);
+    ALICEVISION_LOG_INFO(" - nbOutliersConstraints : " << nbOutliersConstraints);
     ALICEVISION_LOG_INFO(" - somethingErased : " << somethingErased);
     ALICEVISION_LOG_INFO(" - somethingChanged : " << somethingChanged);
 

src/aliceVision/sfm/pipeline/expanding/SfmBundle.hpp

@@ -1,4 +1,5 @@
 // This file is part of the AliceVision project.
+// Copyright (c) 2025 AliceVision contributors.
 // Copyright (c) 2024 AliceVision contributors.
 // This Source Code Form is subject to the terms of the Mozilla Public License,
 // v. 2.0. If a copy of the MPL was not distributed with this file,
@@ -94,6 +95,7 @@ class SfmBundle
     EFeatureConstraint _featureConstraint = EFeatureConstraint::SCALE;
     double _maxReprojectionError = 4.0;
     double _minAngleForLandmark = 2.0;
+    double _maxConstraintDistance = 1.0;
     size_t _minTrackLength = 2;
     size_t _minPointsPerPose = 30;
     size_t _bundleAdjustmentMaxOutlier = 50;

src/aliceVision/sfm/sfmFilters.cpp

@@ -280,5 +280,46 @@ bool eraseUnstablePosesAndObservations(sfmData::SfMData& sfmData,
     return removedPoses || removedObservations;
 }
 
+IndexT removeConstraints(sfmData::SfMData& sfmData, double maxDist)
+{
+    const auto & landmarks = sfmData.getLandmarks();
+    auto & constraints = sfmData.getConstraintsPoint();
+
+    // Remove all constraints which are very far from associated landmark
+
+    size_t count = 0;
+    auto itConstraints = constraints.begin();
+    while (itConstraints != constraints.end())
+    {
+        IndexT trackId = itConstraints->first;
+
+        auto landmarkIt = landmarks.find(trackId);
+
+        //If the associated landmark does not exists anymore, remove the constraint
+        if (landmarkIt == landmarks.end())
+        {
+            itConstraints = constraints.erase(itConstraints);
+            count++;
+            continue;
+        }
+
+        const Vec3 & lpt = landmarkIt->second.X;
+        double dist = (itConstraints->second.point - lpt).norm();
+
+        //Remove if the landmark is too far away
+        if (dist > maxDist)
+        {
+            itConstraints = constraints.erase(itConstraints);
+            count++;
+        }
+        else 
+        {
+            ++itConstraints;
+        }
+    }
+
+    return count;
+}
+
 }  // namespace sfm
 }  // namespace aliceVision

src/aliceVision/sfm/sfmFilters.hpp

@@ -42,6 +42,14 @@ IndexT removeOutliersWithPixelResidualError(sfmData::SfMData& sfmData,
 // Return the number of removed tracks
 IndexT removeOutliersWithAngleError(sfmData::SfMData& sfmData, const double dMinAcceptedAngle);
 
+/**
+ * @Brief remove all point constraints which are too far away from their associated landmark
+ * @param sfmData the sfmData  to update
+ * @param maxDist the maximal allowed distance between the landmark and the constraint
+ * @return the number of constraints removed
+ */
+IndexT removeConstraints(sfmData::SfMData& sfmData, const double maxDist);
+
 bool eraseUnstablePoses(sfmData::SfMData& sfmData, const IndexT minPointsPerPose, std::set<IndexT>* outRemovedViewsId = NULL);
 
 bool eraseObservationsWithMissingPoses(sfmData::SfMData& sfmData, const IndexT minPointsPerLandmark);