Improved performance of function geometry::PointCloud::RemoveRadiusOutliers, function geometry::ClusterDBSCAN and feature counting

cpp/open3d/geometry/PointCloud.cpp

@@ -581,7 +581,8 @@ PointCloud::RemoveRadiusOutliers(size_t nb_points,
     for (int i = 0; i < int(points_.size()); i++) {
         std::vector<int> tmp_indices;
         std::vector<double> dist;
-        size_t nb_neighbors = kdtree.SearchRadius(points_[i], search_radius,
+        size_t nb_neighbors = kdtree.SearchHybrid(points_[i], search_radius,
+                                                  int(nb_points + 1),
                                                   tmp_indices, dist);
         mask[i] = (nb_neighbors > nb_points);
         ++progress_bar;

cpp/open3d/geometry/PointCloudCluster.cpp

@@ -55,33 +55,25 @@ std::vector<int> PointCloud::ClusterDBSCAN(double eps,
             continue;
         }
 
-        std::unordered_set<int> nbs_next(nbs[idx].begin(), nbs[idx].end());
-        std::unordered_set<int> nbs_visited;
-        nbs_visited.insert(int(idx));
-
         labels[idx] = cluster_label;
         ++progress_bar;
+
+        std::vector<int> nbs_next(nbs[idx].begin() + 1, nbs[idx].end());
+
         while (!nbs_next.empty()) {
-            int nb = *nbs_next.begin();
-            nbs_next.erase(nbs_next.begin());
-            nbs_visited.insert(nb);
-
-            // Noise label.
-            if (labels[nb] == -1) {
-                labels[nb] = cluster_label;
-                ++progress_bar;
-            }
-            // Not undefined label.
-            if (labels[nb] != -2) {
+            int nb = nbs_next.back();
+            nbs_next.pop_back();
+
+            if (labels[nb] >= 0) {
                 continue;
             }
             labels[nb] = cluster_label;
             ++progress_bar;
 
             if (nbs[nb].size() >= min_points) {
                 for (int qnb : nbs[nb]) {
-                    if (nbs_visited.count(qnb) == 0) {
-                        nbs_next.insert(qnb);
+                    if (labels[qnb] < 0) {
+                        nbs_next.push_back(qnb);
                     }
                 }
             }

cpp/open3d/pipelines/registration/Feature.cpp

@@ -32,7 +32,7 @@ static Eigen::Vector4d ComputePairFeatures(const Eigen::Vector3d &p1,
     auto n2_copy = n2;
     double angle1 = n1_copy.dot(dp2p1) / result(3);
     double angle2 = n2_copy.dot(dp2p1) / result(3);
-    if (acos(fabs(angle1)) > acos(fabs(angle2))) {
+    if (fabs(angle1) < fabs(angle2)) {
         n1_copy = n2;
         n2_copy = n1;
         dp2p1 *= -1.0;