Unable to directly spawn gltf that does not require components

[GitGhillie]

I want to spawn a scene and because of an issue I ran into (Jondolf/avian#304 if you want more context) I figured I would just spawn it directly during Startup, as this scene doesn't have any components that need to be added using bevy_gltf_components. However, this results in a panic with message "this gltf should have been loaded".

It's not too bad to work around but I'm guessing it's not the intended behavior of the crate.

[czettnersandor]

@GitGhillie how did you workaround this?

[GitGhillie]

@GitGhillie how did you workaround this?

My idea was to use bevy_asset_loader as I do normally with bevy_gltf_components, and then delay spawning one of the scenes like so:

.add_systems(OnEnter(GameState::AssetsLoaded), spawn_A)
.add_systems(
    OnEnter(GameState::AssetsLoaded),
    spawn_B.run_if(on_timer(Duration::new(5, 0))),
)

However, this does not work and only spawns one of A and B... which means the issue I had with bevy_xpbd is maybe an issue with bevy_asset_loader instead. Need to find a different workaround :(

[kaosat-dev]

I want to spawn a scene and because of an issue I ran into (Jondolf/bevy_xpbd#304 if you want more context) I figured I would just spawn it directly during Startup, as this scene doesn't have any components that need to be added using bevy_gltf_components. However, this results in a panic with message "this gltf should have been loaded".

It's not too bad to work around but I'm guessing it's not the intended behavior of the crate.

hmm that is a scenario I did not encounter before, thanks for the bug report !
I think it might make sense to change the way the gltf loading tracking is handled in bevy_gltf_components so that it gives you a warning, and does not blow up in your face/panics.
(this is way overdue, as I also want to deal with dropping un-needed gltf handles that are kept around in the asset tracker).

So changing track_new_gltf (excuse the poor code quality, very tired & sick)

 let handle = asset_server.get_id_handle(*id);
            if let Some(handle) = handle {
                tracker.add_gltf(handle.clone());
                debug!("gltf created {:?}", handle.clone());
            }else {
                warn!("this gltf should have been loaded, no handle available, not processing it")
            }
            ```

[GitGhillie]

That seems to do the trick! Now I'm running into an issue where the scene loaded with the asset loader only rarely shows up, but I think that's then something to do with bevy_asset_loader.

[kaosat-dev]

@GitGhillie is its a random failure of a scene to show up ?
I had such issues back in Bevy 0.11 where scenes would get randomly unloaded directly after being loaded, had not had those issues since then.
Have you tried forcing the creation of a strong handle manually to prevent the issue ?

[GitGhillie]

I made a minimal example to illustrate the problem I'm having with bevy/bevy_asset_loader: https://github.com/GitGhillie/asset_loading_mre/blob/main/src/main.rs

Not sure how to manually create a strong handle but appending #Scene0 to the paths fixes the scenes randomly getting swapped. With my Bevy 0.11 project I was already doing this but now with 0.12 it seems like bevy_gltf_components doesn't work when a scene is spawned with #Scene0. I'm getting "this gltf should have been loaded, no handle available, not processing it" from your hotfix.

[kaosat-dev]

@GitGhillie I suddenly remembered that I faced this issue as well !
When using #scene it unloads the gltf file, the handle is lost, that is why I switched to loading the full gltf files in the examples
I had noted it down as being related to this issue, so it might work on main

[GitGhillie]

Hmm I think the fix for that already lives on 0.12.1 :( When I have more time I'll try to make a minimal reproducer without bevy_asset_loader, then I can also easily test against bevy main

[GitGhillie]

I moved the discussion about asset loading here btw NiklasEi/bevy_asset_loader#182

[kaosat-dev]

Hi @GitGhillie would you mind trying out this pr to see if it solve your issues ?

[GitGhillie]

Looks like it works! I can now load with and without using #Scene0 and with or without components

[kaosat-dev]

Awesome , thanks for trying it out so quickly !