138 lines
5.8 KiB
Markdown
138 lines
5.8 KiB
Markdown
Measurements
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============
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Every frame the server sends a package with the measurements and images gathered
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to the client. This document describes the details of these measurements.
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Time-stamps
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-----------
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Since CARLA can be run at fixed-frame rate, we keep track of two different
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time-stamps.
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Key | Type | Description
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-------------------------- | --------- | ------------
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platform_timestamp | uint32 | Time-stamp of the current frame, in milliseconds as given by the OS.
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game_timestamp | uint32 | In-game time-stamp, milliseconds elapsed since the beginning of the current level.
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In real-time mode, the elapsed time between two time steps should be similar
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both platform and game time-stamps. When run in fixed-time step, the game
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time-stamp increments in constant time steps (delta=1/FPS) while the platform
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time-stamp keeps the actual time elapsed.
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Player measurements
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-------------------
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Key | Type | Description
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-------------------------- | --------- | ------------
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transform | Transform | World transform of the player.
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acceleration | Vector3D | Current acceleration of the player.
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forward_speed | float | Forward speed in km/h.
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collision_vehicles | float | Collision intensity with other vehicles.
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collision_pedestrians | float | Collision intensity with pedestrians.
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collision_other | float | General collision intensity (everything else but pedestrians and vehicles).
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intersection_otherlane | float | Percentage of the car invading other lanes.
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intersection_offroad | float | Percentage of the car off-road.
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autopilot_control | Control | Vehicle's autopilot control that would apply this frame.
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###### Transform
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The transform contains the location and rotation of the player.
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Key | Type | Description
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-------------------------- | ---------- | ------------
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location | Vector3D | World location.
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orientation *[deprecated]* | Vector3D | Orientation in Cartesian coordinates.
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rotation | Rotation3D | Pitch, roll, and yaw.
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###### Collision
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Collision variables keep an accumulation of all the collisions occurred during
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this episode. Every collision contributes proportionally to the intensity of the
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collision (norm of the normal impulse between the two colliding objects).
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Three different counts are kept (pedestrians, vehicles, and other). Colliding
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objects are classified based on their tag (same as for semantic segmentation).
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!!! Bug
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See [#13 Collisions are not annotated when vehicle's speed is low](https://github.com/carla-simulator/carla/issues/13)
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Collisions are not annotated if the vehicle is not moving (<1km/h) to avoid
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annotating undesired collision due to mistakes in the AI of non-player agents.
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###### Lane/off-road intersection
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The lane intersection measures the percentage of the vehicle invading the
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opposite lane. The off-road intersection measures the percentage of the vehicle
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outside the road.
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These values are computed intersecting the bounding box of the vehicle (as a 2D
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rectangle) against the map image of the city. These images are generated in the
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editor and serialized for runtime use. You can find them too in the release
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package under the folder "RoadMaps".
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###### Autopilot control
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The `autopilot_control` measurement contains the control values that the in-game
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autopilot system would apply as if it were controlling the vehicle.
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This is the same structure used to send the vehicle control to the server.
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Key | Type | Description
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-------------------------- | --------- | ------------
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steer | float | Steering angle between [-1.0, 1.0] (*)
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throttle | float | Throttle input between [ 0.0, 1.0]
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brake | float | Brake input between [ 0.0, 1.0]
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hand_brake | bool | Whether the hand-brake is engaged
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reverse | bool | Whether the vehicle is in reverse gear
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To activate the autopilot from the client, send this `autopilot_control` back
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to the server. Note that you can modify it before sending it back.
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```py
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measurements, sensor_data = carla_client.read_data()
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control = measurements.player_measurements.autopilot_control
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# modify here control if wanted.
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carla_client.send_control(control)
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```
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(*) The actual steering angle depends on the vehicle used. The default Mustang
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has a maximum steering angle of 70 degrees (this can be checked in the vehicle's
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front wheel blueprint).
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Non-player agents info
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----------------------
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To receive info of every non-player agent in the scene every frame you need to
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activate this option in the settings file sent by the client at the beginning of
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the episode.
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```ini
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[CARLA/Server]
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SendNonPlayerAgentsInfo=true
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```
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If enabled, the server attaches a list of agents to the measurements package
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every frame. Each of these agents has an unique id that identifies it, and
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belongs to one of the following classes
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* **Vehicle** Contains its transform, box-extent, and forward speed.
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* **Pedestrian** Contains its transform, box-extent, and forward speed. (*)
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* **Traffic light** Contains its transform and state (green, yellow, red).
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* **Speed-limit sign** Contains its transform and speed-limit.
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(*) At this point every pedestrian is assumed to have the same bounding-box
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size.
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###### Transform and bounding box
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The transform defines the location and orientation of the agent. The bounding
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box is assumed to be centered at the agent's location. The box extent gives the
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radii dimensions of the bounding box of the agent.
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!!! important
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As seen in the picture, the Z coordinate of the box is not fitted to
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vehicle's height.
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