Loading heavy resources on demand

[dioptryk]

Godot version:
3.1.1 stable

OS/device including version:
All

Issue description:
I seek the ability to not have all "heavy" resources (like models, textures etc.) loaded immediately upon loading the scene, but on demand, if necessary. Please hear my reasoning before ridiculing me :)

I'm having much fun with Godot since 2.0, experimenting and trying different things, and I finally decided to write a 3d dungeon crawler from first-person perspective, with randomly generated levels. I already have a working PoC and it works very nice. My problem lies with the randomness in relation to the objects to fill level with. Let's say I want to generate a "cave" level. Since caves are all about spiders and such, I'd like to only fill the level with "spider" monsters. Now, I have several types of spiders, each one in a different .tscn, with a specific script, sounds, models, etc. Now, how to actually find all these scenes and choose from them to place a monster?

Attempt 1: Master scene containing all the monsters and a script to get_monster_type. Nice idea, but guess what, all the resources will be loaded anyway with the scene even if I only want a single spider type. Can you see where I'm going with this?

Attempt 2: A custom node tree containing string paths to .tscn files and some metadata, for example biomes the monster appears in etc. Works, but you need to synchronize your library of monsters and the "database", so it's easy to forget something (or specify wrong path). Besides that, you will have redundancy (the database and the monster will definitely share some metadata, so you need to watch out for differences). And you lose self-containment of a monster .tscn, which I just love (a monster is a complete component, that will simply work if placed under a parent that supports it, like a level).

Attempt 3: Editor plugin to scan all monster scenes before running/deploying the game and producing metadata library with all the necessary info about monsters into a .json file. Pretty nice, but still something may break, and besides that, the editor must load everything to scan the .tscn. Besides that, it's still a workaround.

We have this beautiful (I really mean it) editor, which makes it easy to have a game object completely self-contained in a .tscn and I really don't like to being actually forced to make workarounds around it. I was also pretty surprised, that loading PackedScene actually loads everything inside it, even before instantiating it; a lightweight PackedScene would be enough for me (my "database" node tree would reference the monsters, so it could become Autoload without loading all monster resources).

Please comment on my plight, perhaps some of you had similar experience or a better idea?

[Calinou]

I was also pretty surprised, that loading PackedScene actually loads everything inside it, even before instantiating it; a lightweight PackedScene would be enough for me (my "database" node tree would reference the monsters, so it could become Autoload without loading all monster resources).

You can enable Load as Placeholder on specific instanced subscenes by right-clicking them in the Scene Tree dock:

What this will do is turn the instance into an InstancePlaceholder instead of loading the full scene immediately. You can then choose when to actually load the full scene.

Also, support for texture streaming is planned in a future release (likely 4.0 or later).

[dioptryk]

@Calinou This doesn't work in my case, because I need some data from the object and you can't read any property from InstancePlaceholder (I tried it yesterday). For example: you have a Spider.tscn with Monster.gd script attached, and this script has Biomes property, which says where the monster can spawn. You can't read this script property if the scene is a placeholder. You can indeed read it from the dictionary in PackedScene, but then all the data will be loaded, including textures.

[Calinou]

I believe this should be addressed by #36640 as long as you load the resource using a single thread.