NPC Behavior#

Behavior logic of the NPC(non-player-character) is pluggable. If you want to use your own behavior, please see this document.

In this document, we describe how default behavior tree NPC works in traffic environment. Default behavior tree NPC logics are in this package.

List of behaviors#

If you want to check detail, please check documents below.

Entity \ Behavior	Behavior-Tree	Do-Nothing
Vehicle	document	document
Pedestrian	document	document
MiscObject	Does not exist.	Does not exist.

Vehicle NPC (with Behavior-Tree)#

Behavior tree of vehicle NPC is here.

graph TD A[Root]:::behavior --> B(Fallback):::flow B --> C[LaneChange]:::behavior B --> D(Fallback):::flow D --> E[FollowLane]:::behavior D --> F(Fallback):::flow F --> G[FollowFrontEntity]:::behavior F --> H[StopAtTrafficLight]:::behavior F --> I[StopAtStopLine]:::behavior F --> J[StopAtCrossingEntity]:::behavior F --> K[Yield]:::behavior F --> L[MoveBackward]:::behavior classDef behavior fill:#F5AD1A; classDef flow fill:#CFE7E8 click C "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/vehicle/lane_change_action.cpp" click E "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/vehicle/follow_lane_sequence/follow_lane_action.cpp" click G "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/vehicle/follow_lane_sequence/follow_front_entity_action.cpp" click H "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/vehicle/follow_lane_sequence/stop_at_traffic_light_action.cpp" click I "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/vehicle/follow_lane_sequence/stop_at_stop_line_action.cpp" click J "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/vehicle/follow_lane_sequence/stop_at_crossing_entity_action.cpp" click K "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/vehicle/follow_lane_sequence/yield_action.cpp" click L "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/vehicle/follow_lane_sequence/move_backward_action.cpp"

Action	Behavior	Success	Failure
LaneChange	Changing to target lane.	Moved to target lane.	Failed to calculate lane change trajectory.
FollowLane	Following lane and moving to goal.		Lane change was requested, traffic light, stop sing, conflicting entities are detected.
FollowFrontEntity	Following target entity in front of the NPC.	Target entity was disappeared in front of the NPC.
StopAtTrafficLight	Stopping at a traffic light until it becomes green.	The traffic light become green.
StopAtStopLine	Stopping at a stop line.	The NPC was stopped at stop line.	Overrun stop line.
StopAtCrossingEntity	Stopping at crossing entity.	Target entity was crossed.
Yield	Yield to right-of-way entity.	Right of way entity is moved.
MoveBackward	Move backward on lane.	Another request and new goal point was suggested.

Behavior#

LaneChange#

By using API::requestLaneChange function, you send lane change request to target NPC. You can send request with these parameters.

Target#

Value	Meaning
AbsoluteTarget	Changing lanes to the exact target lanelet. You have to specify `lanelet_id`, `offset`
RelativeTarget	Changing lanes to the relative target lanelet. You have to specify `entity_name`, `shift`, `direction`.

AbsoluteTarget#

Value	Meaning	Default
lanelet_id	Lanelet id, which you want to changing lanes to.
offset	Target offset you want to changing lanes.	0

offset value is calculated under lane coordinate.

RelativeTarget#

Value	Meaning	Default
entity_name	Reference entity name.
shift	Number of lanes counted from reference entity name.	0
offset	Target offset you want to changing lanes.	0

TrajectoryShape#

Value	Meaning	Default
CUBIC	Changing lanes with cubic spline trajectory.
LINEAR	Changing lanes with linear trajectory.

Cubic Trajectory Shape#

Linear Trajectory Shape#

Constraint#

Value	Meaning	Default
NONE	Just changing lanes if possible.
LATERAL_VELOCITY	Changing lanes with target lateral velocity.
LONGITUDINAL_DISTANCE	Changing lanes with target longitudinal distance.
TIME	Changing lanes with target duration.

Policy#

Value	Meaning	Default
FORCE	Changing lanes and fulfilling constraints ignoring dynamics.
BEST_EFFORT	Changing lanes and trying to fulfill constraints without ignoring dynamics.

Vehicle NPC (with Do-Nothing)#

When this behavior is used, entity can only be moved by specifying its pose, velocity, acceleration, jerk, etc. via the API::setEntityStatus function, etc.
When using this behavior, any consistency in physical behavior is ignored. Changes in posture, velocity, acceleration, and jerk over time will not occur.
The EntityStatus value will continue to be the value specified and updated via the API::setEntityStatus function, etc.
This behavior was developed primarily to drive the simulator from Autoware rosbag data.

Pedestrian NPC (with Behavior-Tree)#

Behavior tree of pedestrian entity is here.

graph TD A[Root]:::behavior --> B(Fallback):::flow B --> C[FollowLane]:::behavior B --> D[WalkStraight]:::behavior classDef behavior fill:#F5AD1A; classDef flow fill:#CFE7E8 click C "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/pedestrian/follow_lane_action.cpp" click D "https://github.com/tier4/scenario_simulator_v2/blob/master/simulation/behavior_tree_plugin/src/pedestrian/walk_straight_action.cpp"

Action	Behavior	Success	Failure
FollowLane	Entity following the lane which it is exist.
WalkStraight	Entity walk forward and without considering lane.

Pedestrian NPC (with Do-Nothing)#

When this behavior is used, entity can only be moved by specifying its pose, velocity, acceleration, jerk, etc. via the API::setEntityStatus function, etc.
When using this behavior, any consistency in physical behavior is ignored. Changes in posture, velocity, acceleration, and jerk over time will not occur.
The EntityStatus value will continue to be the value specified and updated via the API::setEntityStatus function, etc.
This behavior was developed primarily to drive the simulator from Autoware rosbag data.

Last update: May 1, 2024