Carla 0.10.0 not able to spawn any Walkers.

[NeoGruber]

Setup
Describe the setup you are using to run CARLA along with its version:

• CARLA version: 0.10.0
• Platform: Ubuntu 22.04
• Python version: 3.10
• GPU: RTX 2080
• GPU Drivers: NVIDIA-SMI 560.35.03

Describe the bug
I am failing to spawn Walkers in Carla. Inside the Unreal Project, the different Assets are available. But when I start the Simulation, I am not able to spawn the Pedestrians.

Steps to reproduce
I installed the UE5 dev branch by the Extended build instructions.
And I tried to spawn the walkers by this script:

import carla
import random

client = carla.Client("localhost", 2000)
client.set_timeout(5.0)
world = client.get_world()
map = world.get_map()

spawn_point = random.choice(map.get_spawn_points())
print("Map:", map.name)
print("Spawn Point:", spawn_point)

bp_lib = world.get_blueprint_library()
walker_bp = bp_lib.find("walker.pedestrian.0015")
ai_bp = bp_lib.find("controller.ai.walker")

walker = world.try_spawn_actor(walker_bp, spawn_point)
world.tick()

if walker:
    walker_controller = world.try_spawn_actor(ai_bp, carla.Transform(), walker)
    world.tick()

    if walker_controller:
        walker_controller.start()
        target = world.get_random_location_from_navigation()
        if not target:
            target = spawn_point.location
        walker_controller.go_to_location(target)
        walker_controller.set_max_speed(1.5)
        print("Walker is moving to:", target)
    else:
        print("Failed to spawn controller.")
else:
    print("Failed to spawn walker.")

The output:

 python src/test.py 
Map: Carla/Maps/Town10HD_Opt
Spawn Point: Transform(Location(x=-41.668877, y=48.905540, z=0.600000), Rotation(pitch=0.000000, yaw=-90.161217, roll=0.000000))
Failed to spawn walker.

And on the Carla side:

LogCarla: Error: Actor Description Class is null.
LogCarla: Warning: Failed to spawn actor 'walker.pedestrian.0015'
LogCarla: Error: Actor not Spawned
LogCarlaServer: Responding error: Spawn failed because of invalid actor description

Expected behavior
The Walker should be spawnable.

[batuhanayfer]

I'm having the same problem but with spawning traffic cones. Did you find a fix for it ?

[NeoGruber]

Hey @batuhanayfer, as far as i understood there was a commit 3 Weeks ago that refactored the Actor Factories. For my problem, I managed to track the issue down to the FActorSpawnResult AWalkerActorFactory::SpawnActor method in this commit: ac66720#diff-42c021b581fb5913c53ac02c3c74022d24604689a7c1b377032c5cda65b5b836

FActorSpawnResult AWalkerActorFactory::SpawnActor(
    const FTransform &SpawnAtTransform,
    const FActorDescription &ActorDescription)
{
  FActorSpawnResult SpawnResult;
  if(!IsValid(ActorDescription.Class)) // The actual Actor description class is a nullptr so something wents wrong in the initialization. 
  {
    UE_LOG(LogCarla, Error, TEXT("Actor Description Class is null.")); // this is the log that is the one that crashes
    SpawnResult.Status = EActorSpawnResultStatus::InvalidDescription;
    return SpawnResult;
  }

  AActor* SpawnedActor = GetWorld()->SpawnActor<AActor>(ActorDescription.Class, SpawnAtTransform);
  SpawnResult.Actor = SpawnedActor;

  if(SpawnedActor == nullptr)
  {
    SpawnResult.Status = EActorSpawnResultStatus::Collision;
    return SpawnResult;
  }

  if(PostProcessWalker(SpawnedActor, ActorDescription))
  {
    SpawnResult.Status = EActorSpawnResultStatus::Success;
    return SpawnResult;
  }

  SpawnResult.Status = EActorSpawnResultStatus::UnknownError;
  return SpawnResult;
}

As far as I can guess, something in the LoadWalkerParametersArrayFromFile method wents wrong. I don't have a final fix yet. The commit says there is still wip stuff. So probably there will be a fix soon. :)

TArray<FActorDefinition> AWalkerActorFactory::GetDefinitions()
{
  LoadWalkerParametersArrayFromFile("WalkerParameters.json", WalkersParams); // something wents wrong here? 
  
  UActorBlueprintFunctionLibrary::MakePedestrianDefinitions(WalkersParams, Definitions);
  return Definitions;
}

[nick-bluespace]

I had a similar issue to this. For me it looked like the Unreal Engine cook stage wasn't creating all the artifacts I needed, hence LogCarla: Error: Actor Description Class is null. but the blueprint name is still listed from the config.

Editing Unreal/CarlaUnreal/Config/DefaultGame.ini and adding a new line with +DirectoriesToAlwaysCook=(Path="/Game/Carla/Blueprints/<subdir>") worked for me. In my local build from source in <path>/Build/Release/Package/Carla-0.10.0-Linux-Shipping/Linux/CarlaUnreal/Content/Carla/Blueprints/Walkers/ I don't see artifacts for all the source content in <path>/Unreal/CarlaUnreal/Content/Carla/Blueprints/Walkers so my guess is replacing <subdir> with Walkers might unblock.

I don't have enough insight into the full build process to know if this is a hack or bug somewhere else. If lots of blueprints aren't building correctly I think the always cook logic is smart enough where a single +DirectoriesToAlwaysCook=(Path="/Game/Carla/Blueprints") might capture all the missing runtime artifacts.

[NeoGruber]

Hey @nick-bluespace,

thanks for your advice! Unfortunetly that did not work for me. I also had the issue you described with cars, and there I was able to solve it the same way as you approach, but with the pedestrians I still to get this error.

To clarify my problem: No matter inside the engine or as a coocked binary, I do get the Pedestrian loading issue. So I am pretty sure there is something happening wrong in the loading of the pedestrians.

[zmd-cc]

Got the same issue.
So I changed to use the release instead of build from source by my self, and this goes well.
https://github.com/carla-simulator/carla/releases/tag/0.10.0

Hope it helps.

[NeoGruber]

@zmd-cc

Thanks, but unfortunately it does not...
I have built everything from source in order to customize some things.

[NeoGruber]

@batuhanayfer
SOLVED:
My Issue was because of the different namings of the Walkers inside:
/path/to/your/carla/Unreal/CarlaUnreal/Content/Carla/Config/WalkerParameters.json

And the actual Walkers located in:
/path/to/your/carla/Unreal/CarlaUnreal/Content/Carla/Blueprints/Walkers

Seems like I got an unlucky state of the content in the manual installation instructions:
https://github.com/carla-simulator/carla.git

The replicated bug looks like:

Warning      LogStreaming              LoadPackage: SkipPackage: /Game/Carla/Blueprints/Walkers/BP_AfroF01_v1_G2_FOO (0x4369952E611DB8E0) - The package to load does not exist on disk or in the loader

Which basically lead into the Failure of loading the Pedestrian:

Log          LogCarla                  Spawning actor 'walker.pedestrian.0015'
Error        LogCarla                  Actor Description Class is null.
Warning      LogCarla                  Failed to spawn actor 'walker.pedestrian.0015'
Error        LogCarla                  Actor not Spawned

I think the new Factory functionality offers great extensibility but lacks in terms of a proper error logging. As the bottom error is clearly related to the upper one.

Thanks to all people that participated and tried to Help!