Godot: AnimationNodeStateMachine: Can't travel to '' if state machine is not active.

[Grandro]

Godot version:

3.1

OS/device including version:

Windows

Issue description:

Whenever I try to call the method travel() on AnimationNodeStateMachine I get the error:
'Can't travel to '' if state machine is not active.'

• The AnimationTree is active
• The travel() method gets a valid parameter (one idle and one idle_down for example), but start_request gets reset right before the error is printed, that why I get an empty string.

The AnimationTree consists of 3 StateMachines

each of them are structured like this:

This is my scene structure:

And this is the script on Player:

extends KinematicBody2D

export (int) var walk_speed = 200
export (int) var run_speed = 300
export (int) var frames_till_idle = 300

var state_machines = {}
var curr_speed = 0
var move_state = "idle"
var direction = "down"
var velocity = Vector2(0, 0)

func _ready():
    state_machines["main"] = get_node("AnimationTree").get("parameters/playback")
    state_machines["idle"] = get_node("AnimationTree").get("parameters/idle/playback")
    state_machines["walk"] = get_node("AnimationTree").get("parameters/walk/playback")
    state_machines["run"] = get_node("AnimationTree").get("parameters/run/playback")

func _physics_process(delta):
    _check_movement()
    move_and_slide(velocity)

func _check_movement():

    velocity = Vector2()
    if Input.is_action_pressed("move_down"):
        set_direction("down")
        velocity.y += 1

    if Input.is_action_pressed("move_up"):
        set_direction("up")
        velocity.y -= 1

    if Input.is_action_pressed("move_right"):
        set_direction("right")
        velocity.x += 1

    if Input.is_action_pressed("move_left"):
        set_direction("left")
        velocity.x -= 1

    if velocity.length() > 0:
        if Input.is_action_pressed("move_run"):
            set_move_state("run")
        else:
            set_move_state("walk")

    print(move_state) # prints 'idle' for example
    print(move_state + "_" + direction) # prints 'idle_down' for example
    state_machines["main"].travel(move_state) # prints above error
    state_machines[move_state].travel(move_state + "_" + direction) # prints above error

    velocity = velocity.normalized() * curr_speed

func set_move_state(new_move_state):
    match new_move_state:
        "idle": set_speed(0)
        "walk": set_speed(walk_speed)
        "run": set_speed(run_speed)

    move_state = new_move_state

func set_speed(new_speed):
    curr_speed = new_speed

func set_direction(new_direction):
    direction = new_direction

[mitchcurtis]

I have the same error from what seems to me to be very basic usage. I'm following this video:

https://www.youtube.com/watch?v=0bq2OIjHxk4&

[guilhermefelipecgs]

Please, can you provide a demo project to facilitate debugging?

[Grandro]

Ok, so the system not behaving properly was actually a typos in the state_machines paths, I swapped walk and run.
I made a debug project, these errors are still popping off, most of them at the start of a playtest.
AnimationNodeStateMachine Debug.zip

[guilhermefelipecgs]

'Can't travel to '' if state machine is not active.'

Well, this message is a bit strange, in fact, you need to check if your state machine is already playing before calling travel, like this:

if state_machines["main"].is_playing():
    state_machines["main"].travel(move_state) # prints above error
if state_machines[move_state].is_playing():
    state_machines[move_state].travel(move_state + "_" + direction) # prints above error

[guilhermefelipecgs]

This happens because, when you start the game, only root state machine will be active, sub state machines are only activated after traveling to it.

[Grandro]

Hmm alright... So the only "bug" really is, that the start_request in the source code is cleared before the error message is displayed in animation_node_state_machine.cpp in line 317

[Brayacon]

How did you solve this ?

[robbertzzz]

I just had this issue today, and was only able to solve it by deleting all unused files, all .import files and the entire .import folder. I didn't alter my script that controlled the animations, so it wasn't due to any typos or mistakes in the code. I'm not sure what went wrong, but the issue remained when I removed the AnimationTree node and then added a new one.
I don't have a project I can share unfortunately as I'm working on a project for a client and don't know how to reproduce...

But can confirm the bug definitely still exists on the latest stable build (3.2.1, Windows 10).

[sothys]

This will happen if you have not selected auto-start for one of your nodes in the statemachine root