Scene.Free() doesn't seem to work

KatteKwaaad

Hi friends,

I have built a scene switcher similar as what is shown in the documentation https://docs.godotengine.org/en/3.0/getting_started/step_by_step/singletons_autoload.html, but I am confused as to why my scene are not actually swapping out, but rather rendering op top of the old one, with both active processing and memory consumed.

I have attached a screenshot to show how I am swapping out my scenes: Before scene switch: After scene Switch: You can see the new scene is actually loaded behind the previous one. When I debug in the code, the weird thing is that the 'CurrentScene' object returns null after CurrentScene.Free(), so it does seem to free but I have no clue why it is still showing up.

Below is the code that I use to swap out the scenes, I follow pretty much the same code as with the guidance on the documentation, except that I am trying to keep my root folder, GameWorld, in memory whilst only attaching the new child to that instead. As you can see from the after picture, it overlaps.

public void DeferredGotoScene(string path)
    {
        if (CurrentScene != null)
        {
            //Get parent
            var parentScene = CurrentScene.GetParent();

            // It is now safe to remove the current scene
            CurrentScene.Free();

            // Load a new scene.
            var nextScene = (PackedScene)GD.Load(path);

            // Instance the new scene.
            CurrentScene = nextScene.Instance();

            // Add it to the active scene, as child of parent.
            parentScene.AddChild(CurrentScene);
            //GetTree().Root.AddChild(CurrentScene);

            // Optionally, to make it compatible with the SceneTree.change_scene() API.
            GetTree().CurrentScene = CurrentScene;            
        }
    }

Any advice would be welcome PS: removing the GetTree().CurrentScene on line 22, doesn't seem to affect anything.

Erich_L

I have a strong feeling that CurrentScene isn't holding the object you expect it is.

cybereality

You have to use QueueFree() on objects in the scene tree.

newmodels

Yes call the function queue_free() from the node. It would crash godot if free freed the node at the wrong timing.

KatteKwaaad

I wonder whether how I structured my project might actually be the problem. The way I do my Levels are as such: and the level I wish to transition to: Each of the doors in the levels have an body_shape_entered and exited signal so that I can know when to transition the player. (there is also an animation to open/close the door)

public void OnSpaceDoorTopExitBodyShapeEntered(RID objectEnteredRid, KinematicBody2D objectEntered, int bodyShapeIndex, int localShapeIndex)
    {
        if (objectEntered.Name == "Party")
        {
            //Entered the animation area. Animate door to open
            _spaceDoorSprite.Animation = "open";

            if (localShapeIndex == 1)
            {
                // //Transition
                var sceneManager = GetNode<SceneManager>("/root/GameWorld/SceneManager");
                sceneManager.SwitchScene(TransitionScene, DoorName);                
            }
        }
    }

Now in my SceneManager, there is a SwitchScene method, that does a little bit of a fade animation, with a signal to itself via an AnimationPlayer that will perform the actual switch when the animation complates:

    public void SwitchScene(string scenePath, string doorName)
    {
        TransitionDoorName = doorName;
        TransitionPath = scenePath;
        var animationPlayer = GetNode<AnimationPlayer>("AnimationPlayer");
        animationPlayer.Play("fade_to_black");
        GD.Print("Fading to black");
    }

    private void OnAnimationPlayerAnimationFinished(string animationName)
    {
        if (string.Equals(animationName, "fade_to_black"))
        {
            GD.Print("Faded to black");
            //EmitSignal(nameof(Transitioned), "fade_to_black");            
            var animationPlayer = GetNode<AnimationPlayer>("AnimationPlayer");
            animationPlayer.Play("fade_to_normal");
            //EmitSignal(nameof(Transitioned));
            //GD.Print("Signal transmitted");
            GotoScene(TransitionPath);

        }
        if (string.Equals(animationName, "fade_to_normal"))
        {
            GD.Print("Finished fading");
        }
    }

I've already posted the 'GotoScene' method above.

So these doors call into the SceneManager node, that sits under the GameWorld Node /root/GameWorld/SceneManager and when switched out, should change,for example, /root/GameWorld/BFZuluQuarters with /root/GameWorld/BFZuluWestHallway. Each of the Levels have code in the _Ready function to determine where to spawn the player:

    public override void _Ready()
    {
        
        var sceneManager = GetNode<SceneManager>("/root/GameWorld/SceneManager");        
        if (!string.IsNullOrWhiteSpace(sceneManager.TransitionDoorName))
        {
            var playerNode = GetNode<Party>("Party");
            if (string.Equals(sceneManager.TransitionDoorName, "QuartersDoor"))
            {
                playerNode.Position = new Vector2(480,416);
            }
        }
    }

Could it be that these doors, which sit inside each levels, that call out to the Singleton/Autoloaded SceneManager, to replace its own parent level, that causes this effect? I would imagine if a child node calls out to a grandparent/higher up node to replace its own parent is not an issue.

cybereality

Did you read the posts above? I think QueueFree() may help you.

KatteKwaaad

@cybereality said: Did you read the posts above? I think QueueFree() may help you.

Apologies, I did try it but the result was the same.

cybereality

On the left side of the Godot editor, right on top of the scene tree is a button that says Remote. If you press it, you can see what nodes exist in the game, before and after you switch scenes. It may give you a clue as to the problem.

KatteKwaaad

@cybereality said: On the left side of the Godot editor, right on top of the scene tree is a button that says Remote. If you press it, you can see what nodes exist in the game, before and after you switch scenes. It may give you a clue as to the problem.

You helped me find the issue with that tip of Remote. I noticed that my GameWorld was loaded in twice because I added it as a Singleton. My wrongful assumption was that you won't be able to load duplicates but there it was, along with the children on 2 separate scene trees!

I refactored my project and have learned from this mistake! Thanks once again for the tip on the Remote scene debugger, as you probably noticed, I am very new to Godot.

cybereality

So glad I could help.