Populate the scene with actors#

About Actor Movement System#

Actor Movement System, aka AMS, is an Unreal Engine plugin made by Parrot. It allows the end-user to put one or more moving targets inside the scene and make them move along a predefined path.

These moving targets can be of several shapes. So far, human pedestrians and vehicles are supported.

In every UE4 applications provided with Parrot Sphinx, one or several “paths” is included. There is systematically a path called DefaultPath. By default, they are visible at runtime with Unreal cameras.

Command line arguments#

The control of the plugin is done through the application’s command line. Here are the available parameters to pass.

-list-actors This command shows the available pedestrians that can be used.

$ parrot-ue4-empty -list-actors
LogAMS: Display: == Available Characters ======================================
LogAMS: Display: - Stefani
LogAMS: Display: - Jasper
LogAMS: Display: - Malcolm
LogAMS: Display: == Available Vehicles ========================================
LogAMS: Display: - BoxTruck
LogAMS: Display: - Hatchback
LogAMS: Display: - Pickup
LogAMS: Display: - SUV
LogAMS: Display: - SportsCar
LogAMS: Display: ==============================================================

-list-paths This command shows the different paths present in the world.

$ parrot-ue4-empty -list-paths
LogAMS: Display: == Available Paths ========================================
LogAMS: Display: Path name : DefaultPath
LogAMS: Display: Path name : RunPath
LogAMS: Display: ===========================================================

-ams-path=<PathName>,<Actor1[:<drone>]>[,<Actor2>,...] This command tells the plugin to spawn N moving targets along the path called “PathName”. You can append several “-ams-path”s in the same command line.

When several actors are set in the same path, they will be spawned evenly all along the path so that the risk of collision gets reduced. That being said, if the actors do not have the same speed, collisions are likely to happen.

To have one actor being tracked by a drone, you need to append “:<drone_name>” after the name of the actor. The Wildcard ‘*’ can be used if you do not want to bother with giving the right drone name. In that case, the first drone found in the simulation will be taken. Once an actor is tracked, its GPS and barometer information will be injected to the drone firmware at the place of the drone controller’s.

Command line example:
```
$ parrot-ue4-empty -ams-path=DefaultPath,Pickup:* -ams-path=RunPath,Jasper
```

Note

It is not possible to assign a given drone to several actors at the same time. As a consequence, the wildcard ‘*’ should be used only once in the command line.

If you want to spawn pedestrians and vehicles on the same path, pedestrians would be spawned before vehicles even if you write the vehicles names at first in the command line. This order was chosen to avoid any unwanted collision between a vehicle and a pedestrian because of their different speed.

For example:

$ parrot-ue4-empty -ams-path=DefaultPath,Pickup,SUV,Jasper,Malcolm

-list-actor-spawn-points This command shows the available spawn points used to take off from vehicles, the command shows the name, location and rotation of each point. Note that you should tell the app which vehicles you want to spawn to be able to show their take off spawn points.

Command line example:

$ parrot-ue4-empty -ams-path=DefaultPath,Pickup,SUV -list-actor-spawn-points
LogAMS: Display: == Available Spawn Points for vehicles =======================
LogAMS: Display: - Name: Pickup
LogAMS: Display:   Pose: 4.400000 21.600000 1.800000 0.000000 0.000000 0.000000
LogAMS: Display: - Name: SUV
LogAMS: Display:   Pose: 73.079308 0.059026 2.800000 0.000000 0.000000 68.622078
LogAMS: Display: ==============================================================

Take off from vehicle using AMS#

First you need to spawn a vehicle using AMS then you need to specify the name of that vehicle using the command line argument ::pose=

Command line example:

$ sphinx <my.drone>::pose="pickup" & parrot-ue4-empty -ams-path=DefaultPath,Pickup

Spawn drone near pedestrians#

First you need to spawn a pedestrian using AMS then you need to specify his name using the command line argument ::pose=, same thing as vehicles. The drone are spawned 1 meter behind the selected pedestrian.

Command line example:

$ sphinx <my.drone>::pose="Jasper" & parrot-ue4-empty -ams-path=DefaultPath,Jasper

Attaching tags to vehicles#

Vehicles can have a visual tag placed on their roof. Once you spawn one or several vehicles, you can set the same tag to all of them using the web dashboard (or sphinx-cli). The parameter tags_name takes the name of the desired texture. The list of available textures is below.

aruco
parrot_logo
h_boost
h_logo
rotational_invariant_dil
white_logo
empty string will hide the tag
wrong name will hide the tag with an error

Here’s a command line example to set the tags_name parameter:

$ sphinx-cli param -m world actors tags_name parrot_logo

The parameter tags_material takes the name of the desired material to use with the tag. The list of available materials is below.

Default
NoReflections

Wrong material name will display an error in the terminal. Here’s a command line example to set the tags_material parameter:

$ sphinx-cli param -m world actors tags_material NoReflections

By default, all tags have the dimension of a paper sheet. However, these dimensions can be changed by setting the parameters tags_width and tags_height using the Web dashboard or sphinx-cli. Note: values are expressed in cm.

Here’s a command line example :

$ sphinx-cli param -m world actors tags_width 40
$ sphinx-cli param -m world actors tags_height 30

The parameters tags_offset_x, tags_offset_y and tags_offset_z add offsets to the tag’s location in its local reference frame. Note: Values are expressed in cm.

Here’s a command line example to shift the position of the current tag:

$ sphinx-cli param -m world actors tags_offset_x 5
$ sphinx-cli param -m world actors tags_offset_y 10
$ sphinx-cli param -m world actors tags_offset_z 20

Note

Changing the tag’s location by editing the parameter tags_location resets all offsets.

Lift actor’s hand#

In addition of standing, walking and running, a pedestrian can lift his right hand to a 90° angle.

First you need to spawn a pedestrian using AMS. Then using the web dashboard (or sphinx-cli), you can set the parameter lift_hand to raise/lower the actor’s arm.

Note

The pedestrian must be in pause mode to be able to lift his hand.

Here’s a command line example to set the lift_hand parameter:

$ sphinx-cli param -m world actors lift_hand true

It’s also possible to land on the actor’s hand.

Change tracked actor#

If you have populated your scene with more than one actor, you can switch tracking from one to another.

First, you need to spawn more than one actor using AMS.

$ parrot-ue4-empty -ams-path=DefaultPath,Pickup:* -ams-path=RunPath,Jasper

A description containing populated paths and their actors should appear once the simulation is launched.

== Paths details ===========================================
Path 'DefaultPath' includes Pickup_0
Path 'RunPath' includes Jasper_0
==============================================================

Now using the web dashboard (or sphinx-cli), you can set the actor_to_track parameter to change the tracked actor (or to start tracking a new one).

Here’s a command line example to set the actor_to_track parameter:

$ sphinx-cli param -m world actors actor_to_track Jasper_0

Customization of AMS#

You can customize some aspects of the AMS feature by bringing a YAML configuration file to UE4 app’s command line, as follows.

$ parrot-ue4-empty -config-file=</path/to/file.yaml>

Respecting the YAML format, an AMS configuration file could look like that:

Paths:
  - Name: 'MyAwesomePath'
    SplinePoints:
      - 1.85 -9.5 0.4 Walk 15
      - 15.76 -10.10 0.4 Run 20
      - 17.635 0.85 0.4 Stop 5
      - 17.02 12.03 0.4 Run 20
      - 3.03 14.92 0.4 Walk 15
    ClosedLoop: true
Tags:
  - Name: 'MyAwesomeTag'
    FilePath: '/path/to/MyAwesomeTag.png'
    Width : 30
    Height : 25
    OffsetZ : 10
  - Name: 'MyEvenMoreAwesomeTag'
    FilePath: '/path/to/MyEvenMoreAwesomeTag.png'
    Location : 'Roof'
    Width : 50
    Height : 30
    OffsetX : 10
    OffsetY : 5
    OffsetZ : 20

Two element types can be modified: the paths and the vehicle tags.

Creating custom paths#

As shown in the configuration example, all path definitions belong to the same dictionary entry Paths. Each path definition must have the following fields:

Name- The name of the path.

Make sure that you don’t choose an already existing path name. You can use the command line -list-paths to visualize the existing paths.
SplinePoints - A list of the different waypoints of the path. Each
waypoint is a string containing a location [x y z], an optional attitude, and an optional vehicle speed.

The location [x y z] is expressed in Gazebo’s coordinate system. You can use the Unreal app’s report window (key P) to visualize and retrieve the Gazebo coordinates of any desired point in the world.

The optional attitude defines the behavior of the pedestrian beyond the related waypoint. It can be:
- Walk: Asks the pedestrian to walk (default value).
- Run: Asks the pedestrian to run.
- Stop: Asks the pedestrian to stop for 5 seconds then start walking towards the next waypoint.
The optional vehicle speed defines the new target speed in km/h for vehicles beyond the related waypoint. The default value is 15 km/h. The maximum speed for vehicles is 150 km/h.
Note

The proportional-integral-derivative controller (PID controller) used to control the vehicle speed is configured to converge relatively fast. Therefore, it is recommended to limit the speed variation between two successive waypoints.
ClosedLoop - A boolean that defines whether the path is a closed loop
or not.

To use the custom path given in the example above, just do like with the predefined paths:

$ parrot-ue4-empty -config-file=</path/to/file.yaml> -ams-path=MyAwesomePath,Jasper

Loading custom tags#

As shown in the configuration example, all tag definitions belong to the same dictionary entry Tags. Each tag definition must have the following fields:

Name- The name of the tag.
FilePath- The absolute path to the png file.
Width - The width of the tag in centimeters.
Height- The height of the tag in centimeters.
Location - (optional) A string that specifies the position of the tag on the vehicle from a list of a predefined positions for each vehicle. Every single vehicle has a tag location named Default, which is the location used when nothing or something wrong is given. The images below show all the available tag positions and names for each vehicle.
- Pickup
- Suv
- SportsCar
- Hatchback
- BoxTruck
OffsetX - The offset, in centimeters, added the tag’s location following the X axis in its local reference frame.
OffsetY - The offset, in centimeters, added the tag’s location following the Y axis in its local reference frame.
OffsetZ - The offset, in centimeters, added the tag’s location following the Z axis in its local reference frame.

To use the custom tag MyAwesomeTag defined in the example above:

$ parrot-ue4-empty -config-file=</path/to/file.yaml> -ams-path=DefaultPath,Pickup
$ sphinx-cli param -m world actors tags_name MyAwesomeTag