Scene vs World, Asset vs Resource, Entity vs Object

[LastExceed]

Total beginner, I'm struggling a bit with the terminology. What's what?

[Zentropivity]

This is good read that may answer some questions: https://docs.rs/bevy/latest/bevy/ecs/index.html

How I look at it:

• World contains all the data, including entities and their components, resources, ...
• Think of Entities as references to objects (there is no such thing as Object that I know in bevy). They are empty/behaviorless until you add Components to them.
  The behavior of an entity is defined by what components are on it. To program that behavior you can make systems.
• Resources are things that are stored globally, not on individual entities. They can also be accessed/changed by systems.
• Asset is mostly used to load data like pictures, 3D models and whatever files you may use. You could write an asset loader for custom assets.

[Igor-dvr]

Bevy guides https://taintedcoders.com/

[LastExceed]

Sorry, I realize I should have been a bit more specific. I have of course tried googling this before posting. What I struggle to understand is specifically the differences. E.g.

Resources are things that are stored globally, not on individual entities

To my understanding, assets are also stored globally instead of per-entity, so my question is: whats the difference? the only answer i can find is that assets are expensive to load, but this alone doesnt seem like enough reason to introduce a whole separate concept

Similarly, how is a scene fundamentally different from a hierachy of entities?

This isnt meant as critique or anything, I'm just trying to understand

[Zentropivity]

Assets use resources for storage. Their main point is loading data from disk and efficiently sharing it using Handles.
For example, 3D geometry (mesh) is not stored directly in a component on the entity, the component stores a handle to the asset: Mesh3d. I suppose it makes sense to do it this way when you would have multiple entities with the same mesh.

Scenes are a way to save and load the state of the world including entities and their components so you can store a hierarchy of entities in it if you choose to. They can be loaded as assets from disk from .scn.ron files and they can also be saved as such.
There is an example on usage here.

[LastExceed]

Ok, just to double-check if I understood this right:

Does this mean an asset IS an (expensive-to-load) resource, rather than a separate concept?

And likewise, a scene IS a (serializable) hierachy of entities?

[Zentropivity]

I would call assets a separate, higher level concept.
I don't actually know how expensive asset loading is... you could say reading files from disk is expensive.
The provided mechanisms to load audio, image and other files from disk use assets. It is implemented using Resource (Assets<...> for each type of asset) and there are lifecycle events for when assets change.

Yes, Scene is a serializable hierarchy of entities, that is my understanding of it.

Personally I found that assets can have other uses than loading files from disk...

I am experimenting with making an SVG editor where I'm considering making custom palette colors Asset. I would make my color asset editable and change could be handled in a system to update each entity that uses it.