Make LocalTrajectoryBuilder optional. (#799)

This is to prepare for the cloud-based mapping case where the robot is running cartographer in pure-localization mode and the cloud instance only solves the global problem. In that case a `LocalTrajectoryBuilder` need to be instantiated in for the cloud instance.

cartographer/internal/mapping/global_trajectory_builder.h

@@ -28,13 +28,15 @@ template <typename LocalTrajectoryBuilder,
           typename LocalTrajectoryBuilderOptions, typename PoseGraph>
 class GlobalTrajectoryBuilder : public mapping::TrajectoryBuilderInterface {
  public:
+  // Passing a 'nullptr' for 'local_trajectory_builder' is acceptable, but no
+  // 'TimedPointCloudData' may be added in that case.
   GlobalTrajectoryBuilder(
-      const LocalTrajectoryBuilderOptions& options, const int trajectory_id,
+      std::unique_ptr<LocalTrajectoryBuilder> local_trajectory_builder,
-      PoseGraph* const pose_graph,
+      const int trajectory_id, PoseGraph* const pose_graph,
       const LocalSlamResultCallback& local_slam_result_callback)
       : trajectory_id_(trajectory_id),
         pose_graph_(pose_graph),
-        local_trajectory_builder_(options),
+        local_trajectory_builder_(std::move(local_trajectory_builder)),
         local_slam_result_callback_(local_slam_result_callback) {}
   ~GlobalTrajectoryBuilder() override {}
 
@@ -44,8 +46,10 @@ class GlobalTrajectoryBuilder : public mapping::TrajectoryBuilderInterface {
   void AddSensorData(
       const std::string& sensor_id,
       const sensor::TimedPointCloudData& timed_point_cloud_data) override {
+    CHECK(local_trajectory_builder_)
+        << "Cannot add TimedPointCloudData without a LocalTrajectoryBuilder.";
     std::unique_ptr<typename LocalTrajectoryBuilder::MatchingResult>
-        matching_result = local_trajectory_builder_.AddRangeData(
+        matching_result = local_trajectory_builder_->AddRangeData(
             timed_point_cloud_data.time,
             sensor::TimedRangeData{timed_point_cloud_data.origin,
                                    timed_point_cloud_data.ranges,
@@ -71,14 +75,18 @@ class GlobalTrajectoryBuilder : public mapping::TrajectoryBuilderInterface {
 
   void AddSensorData(const std::string& sensor_id,
                      const sensor::ImuData& imu_data) override {
-    local_trajectory_builder_.AddImuData(imu_data);
+    if (local_trajectory_builder_) {
+      local_trajectory_builder_->AddImuData(imu_data);
+    }
     pose_graph_->AddImuData(trajectory_id_, imu_data);
   }
 
   void AddSensorData(const std::string& sensor_id,
                      const sensor::OdometryData& odometry_data) override {
     CHECK(odometry_data.pose.IsValid()) << odometry_data.pose;
-    local_trajectory_builder_.AddOdometryData(odometry_data);
+    if (local_trajectory_builder_) {
+      local_trajectory_builder_->AddOdometryData(odometry_data);
+    }
     pose_graph_->AddOdometryData(trajectory_id_, odometry_data);
   }
 
@@ -95,7 +103,7 @@ class GlobalTrajectoryBuilder : public mapping::TrajectoryBuilderInterface {
  private:
   const int trajectory_id_;
   PoseGraph* const pose_graph_;
-  LocalTrajectoryBuilder local_trajectory_builder_;
+  std::unique_ptr<LocalTrajectoryBuilder> local_trajectory_builder_;
   LocalSlamResultCallback local_slam_result_callback_;
 };
 

cartographer/mapping/map_builder.cc

@@ -75,27 +75,37 @@ int MapBuilder::AddTrajectoryBuilder(
     LocalSlamResultCallback local_slam_result_callback) {
   const int trajectory_id = trajectory_builders_.size();
   if (options_.use_trajectory_builder_3d()) {
-    CHECK(trajectory_options.has_trajectory_builder_3d_options());
+    std::unique_ptr<mapping_3d::LocalTrajectoryBuilder>
+        local_trajectory_builder;
+    if (trajectory_options.has_trajectory_builder_3d_options()) {
+      local_trajectory_builder =
+          common::make_unique<mapping_3d::LocalTrajectoryBuilder>(
+              trajectory_options.trajectory_builder_3d_options());
+    }
     trajectory_builders_.push_back(
         common::make_unique<CollatedTrajectoryBuilder>(
             &sensor_collator_, trajectory_id, expected_sensor_ids,
             common::make_unique<mapping::GlobalTrajectoryBuilder<
                 mapping_3d::LocalTrajectoryBuilder,
                 mapping_3d::proto::LocalTrajectoryBuilderOptions,
-                mapping_3d::PoseGraph>>(
+                mapping_3d::PoseGraph>>(std::move(local_trajectory_builder),
-                trajectory_options.trajectory_builder_3d_options(),
                                         trajectory_id, pose_graph_3d_.get(),
                                         local_slam_result_callback)));
   } else {
-    CHECK(trajectory_options.has_trajectory_builder_2d_options());
+    std::unique_ptr<mapping_2d::LocalTrajectoryBuilder>
+        local_trajectory_builder;
+    if (trajectory_options.has_trajectory_builder_2d_options()) {
+      local_trajectory_builder =
+          common::make_unique<mapping_2d::LocalTrajectoryBuilder>(
+              trajectory_options.trajectory_builder_2d_options());
+    }
     trajectory_builders_.push_back(
         common::make_unique<CollatedTrajectoryBuilder>(
             &sensor_collator_, trajectory_id, expected_sensor_ids,
             common::make_unique<mapping::GlobalTrajectoryBuilder<
                 mapping_2d::LocalTrajectoryBuilder,
                 mapping_2d::proto::LocalTrajectoryBuilderOptions,
-                mapping_2d::PoseGraph>>(
+                mapping_2d::PoseGraph>>(std::move(local_trajectory_builder),
-                trajectory_options.trajectory_builder_2d_options(),
                                         trajectory_id, pose_graph_2d_.get(),
                                         local_slam_result_callback)));
   }