#gamedev #bevy #gltf #blueprint #prefab

bevy_gltf_blueprints

Adds the ability to define Blueprints/Prefabs for Bevy inside gltf files and spawn them in Bevy

19 releases (6 breaking)

new 0.7.3 Feb 19, 2024
0.6.0 Jan 10, 2024
0.5.1 Dec 27, 2023
0.3.3 Nov 25, 2023

#134 in Game dev

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946 downloads per month
Used in bevy_gltf_save_load

MIT/Apache

62KB
757 lines

Crates.io Docs License Bevy tracking

bevy_gltf_blueprints

Built upon bevy_gltf_components this crate adds the ability to define Blueprints/Prefabs for Bevy inside gltf files and spawn them in Bevy.

  • Allows you to create lightweight levels, where all assets are different gltf files and loaded after the main level is loaded
  • Allows you to spawn different entities from gtlf files at runtime in a clean manner, including simplified animation support !

A blueprint is a set of overrideable components + a hierarchy: ie

* just a Gltf file with Gltf_extras specifying components 
* a component called BlueprintName

Particularly useful when using Blender as an editor for the Bevy game engine, combined with the Blender plugin that does a lot of the work for you

Usage

Here's a minimal usage example:

# Cargo.toml
[dependencies]
bevy="0.12"
bevy_gltf_blueprints = { version = "0.7"} 

use bevy::prelude::*;
use bevy_gltf_blueprints::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugins(BlueprintsPlugin)

        .run();
}

// not shown here: any other setup that is not specific to blueprints

fn spawn_blueprint(
    mut commands: Commands,
    keycode: Res<Input<KeyCode>>,
){
    if keycode.just_pressed(KeyCode::S) {
        let new_entity = commands.spawn((
            BlueprintName("Health_Pickup".to_string()), // mandatory !!
            SpawnHere, // mandatory !!
            TransformBundle::from_transform(Transform::from_xyz(x, 2.0, y)), // VERY important !!
            // any other component you want to insert
        ));
    }
}

Installation

Add the following to your [dependencies] section in Cargo.toml:

bevy_gltf_blueprints = "0.7"

Or use cargo add:

cargo add bevy_gltf_blueprints

Setup

use bevy::prelude::*;
use bevy_gltf_blueprints::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugin(BlueprintsPlugin)

        .run();
}

you may want to configure your "library"/"blueprints" settings:

use bevy::prelude::*;
use bevy_gltf_blueprints::*;

fn main() {
    App::new()
        .add_plugins((
             BlueprintsPlugin{
                library_folder: "advanced/models/library".into() // replace this with your blueprints library path , relative to the assets folder,
                format: GltfFormat::GLB,// optional, use either  format: GltfFormat::GLB, or  format: GltfFormat::GLTF, or  ..Default::default() if you want to keep the default .glb extension, this sets what extensions/ gltf files will be looked for by the library
                aabbs: true, // defaults to false, enable this to automatically calculate aabb for the scene/blueprint
                material_library: true,  // defaults to false, enable this to enable automatic injection of materials from material library files
                material_library_folder: "materials".into() //defaults to "materials" the folder to look for for the material files
                ..Default::default()
            }
        ))
        .run();
}

Spawning entities from blueprints

You can spawn entities from blueprints like this:

commands.spawn((
    BlueprintName("Health_Pickup".to_string()), // mandatory !!
    SpawnHere, // mandatory !!
    
    TransformBundle::from_transform(Transform::from_xyz(x, 2.0, y)), // optional
    // any other component you want to insert
))

Once spawning of the actual entity is done, the spawned Blueprint will be gone/merged with the contents of Blueprint !

Important : you can add or override components present inside your Blueprint when spawning the BluePrint itself: ie

Adding components not specified inside the blueprint

you can just add any additional components you need when spawning :

commands.spawn((
    BlueprintName("Health_Pickup".to_string()),
    SpawnHere,
    TransformBundle::from_transform(Transform::from_xyz(x, 2.0, y)),
    // from Rapier/bevy_xpbd: this means the entity will also have a velocity component when inserted into the world
    Velocity {
        linvel: Vec3::new(vel_x, vel_y, vel_z),
        angvel: Vec3::new(0.0, 0.0, 0.0),
      },
))

Overriding components specified inside the blueprint

any component you specify when spawning the Blueprint that is also specified within the Blueprint will override that component in the final spawned entity

for example

commands.spawn((
    BlueprintName("Health_Pickup".to_string()),
    SpawnHere,
    TransformBundle::from_transform(Transform::from_xyz(x, 2.0, y)),
    HealthPowerUp(20)// if this is component is also present inside the "Health_Pickup" blueprint, that one will be replaced with this component during spawning
))

BluePrintBundle

There is also a bundle for convenience , which just has

  • a BlueprintName component
  • a SpawnHere component

BluePrintBundle

Additional information

  • When a blueprint is spawned, all its children entities (and nested children etc) also have an InBlueprint component that gets insert
  • In cases where that is undesirable, you can add a NoInBlueprint component on the entity you spawn the blueprint with, and the components above will not be add
  • if you want to overwrite the path where this crate looks for blueprints (gltf files) , you can add a Library component , and that will be used instead of the default path ie :
commands
    .spawn((
        Name::from("test"),
        BluePrintBundle {
            blueprint: BlueprintName("TestBlueprint".to_string()),
            ..Default::default()
        },
        Library("models".into()) // now the path to the blueprint above will be /assets/models/TestBlueprint.glb
    ))
  • this crate also provides a special optional GameWorldTag component: this is useful when you want to keep all your spawned entities inside a root entity

You can use it in your queries to add your entities as children of this "world" This way all your levels, your dynamic entities etc, are kept seperated from UI nodes & other entities that are not relevant to the game world

Note: you should only have a SINGLE entity tagged with that component !

    commands.spawn((
        SceneBundle {
            scene: models
                .get(game_assets.world.id())
                .expect("main level should have been loaded")
                .scenes[0]
                .clone(),
            ..default()
        },
        bevy::prelude::Name::from("world"),
        GameWorldTag, // here it is
    ));

SystemSet

the ordering of systems is very important !

For example to replace your proxy components (stand-in components when you cannot/ do not want to use real components in the gltf file) with actual ones, which should happen AFTER the Blueprint based spawning,

so bevy_gltf_blueprints provides a SystemSet for that purpose:GltfBlueprintsSet

Typically , the order of systems should be

bevy_gltf_components (GltfComponentsSet::Injection) => bevy_gltf_blueprints (GltfBlueprintsSet::Spawn, GltfBlueprintsSet::AfterSpawn) => replace_proxies

see https://github.com/kaosat-dev/Blender_bevy_components_workflow/tree/main/examples/bevy_gltf_blueprints/basic for how to set it up correctly

Animation

bevy_gltf_blueprints provides some lightweight helpers to deal with animations stored in gltf files

  • an Animations component that gets inserted into spawned (root) entities that contains a hashmap of all animations contained inside that entity/gltf file . (this is a copy of the named_animations inside Bevy's gltf structures )
  • an AnimationPlayerLink component that gets inserted into spawned (root) entities, to make it easier to trigger/ control animations than it usually is inside Bevy + Gltf files

The workflow for animations is as follows:

  • create a gltf file with animations (using Blender & co) as you would normally do
  • inside Bevy, use the bevy_gltf_blueprints boilerplate (see sections above), no specific setup beyond that is required
  • to control the animation of an entity, you need to query for entities that have both AnimationPlayerLink and Animations components (added by bevy_gltf_blueprints) AND entities with the AnimationPlayer component

For example:

// example of changing animation of entities based on proximity to the player, for "fox" entities (Tag component)
pub fn animation_change_on_proximity_foxes(
    players: Query<&GlobalTransform, With<Player>>,
    animated_foxes: Query<(&GlobalTransform, &AnimationPlayerLink, &Animations ), With<Fox>>,

    mut animation_players: Query<&mut AnimationPlayer>,

){
    for player_transforms in players.iter() {
        for (fox_tranforms, link, animations) in animated_foxes.iter() {
            let distance = player_transforms
                .translation()
                .distance(fox_tranforms.translation());
            let mut anim_name = "Walk"; 
            if distance < 8.5 {
                anim_name = "Run"; 
            }
            else if distance >= 8.5 && distance < 10.0{
                anim_name = "Walk";
            }
            else if distance >= 10.0 && distance < 15.0{
                anim_name = "Survey";
            }
            // now play the animation based on the chosen animation name
            let mut animation_player = animation_players.get_mut(link.0).unwrap();
            animation_player.play_with_transition(
                animations.named_animations.get(anim_name).expect("animation name should be in the list").clone(), 
                Duration::from_secs(3)
            ).repeat();
        }
    }
}

see https://github.com/kaosat-dev/Blender_bevy_components_workflow/tree/main/examples/bevy_gltf_blueprints/animation for how to set it up correctly

particularly from https://github.com/kaosat-dev/Blender_bevy_components_workflow/tree/main/examples/bevy_gltf_blueprints/animation/game/in_game.rs#86 onward

Materials

You have the option of using "material libraries" to share common textures/materials between blueprints, in order to avoid asset & memory bloat:

Ie for example without this option, 56 different blueprints using the same material with a large texture would lead to the material/texture being embeded 56 times !!

you can configure this with the settings:

material_library: true  // defaults to false, enable this to enable automatic injection of materials from material library files
material_library_folder: "materials".into() //defaults to "materials" the folder to look for for the material files

Important! you must take care of preloading your material librairy gltf files in advance, using for example bevy_asset_loadersince bevy_gltf_blueprints currently does NOT take care of loading those at runtime

see https://github.com/kaosat-dev/Blender_bevy_components_workflow/tree/main/examples/bevy_gltf_blueprints/materials for how to set it up correctly

Generating optimised blueprints and material libraries can be automated using the latests version of the Blender plugin

Legacy mode

Starting in version 0.7 there is a new parameter legacy_mode for backwards compatibility

To disable the legacy mode: (enabled by default)

BlueprintsPlugin{legacy_mode: false}

You need to disable legacy mode if you want to use the bevy_components Blender addon + the bevy_registry_export crate ! As it create custom properties that are writen in real ron file format instead of a simplified version (the one in the legacy mode)

Note: the legacy mode support will be dropped in future versions, and the default behaviour will be NO legacy mode

Examples

https://github.com/kaosat-dev/Blender_bevy_components_workflow/tree/main/examples/bevy_gltf_blueprints/basic

https://github.com/kaosat-dev/Blender_bevy_components_workflow/tree/main/examples/bevy_gltf_blueprints/basic_xpbd_physics

https://github.com/kaosat-dev/Blender_bevy_components_workflow/tree/main/examples/bevy_gltf_blueprints/animation

https://github.com/kaosat-dev/Blender_bevy_components_workflow/tree/main/examples/bevy_gltf_blueprints/materials

https://github.com/kaosat-dev/Blender_bevy_components_workflow/tree/main/examples/bevy_gltf_blueprints/multiple_levels_multiple_blendfiles

Compatible Bevy versions

The main branch is compatible with the latest Bevy release, while the branch bevy_main tries to track the main branch of Bevy (PRs updating the tracked commit are welcome).

Compatibility of bevy_gltf_blueprints versions:

bevy_gltf_blueprints bevy
0.3 - 0.7 0.12
0.1 - 0.2 0.11
branch main 0.12
branch bevy_main main

License

This crate, all its code, contents & assets is Dual-licensed under either of

Dependencies

~41–81MB
~1M SLoC