Async colliders

[Jondolf]

Objective

Fixes #104. Depends on #154 and #189.

Currently, there's no easy way to add colliders to meshes loaded from scenes (glTFs and so on). A very common request is to have a way to generate the colliders automatically.

Solution

Add AsyncCollider and AsyncSceneCollider, which are essentially equivalents to bevy_rapier's components. Also add a ComputedCollider enum that determines if the colliders should be trimeshes or convex hulls. Because these rely on some Bevy features, there is a new async-collider feature that is enabled by default, but only in 3D because colliders can't be created from meshes in 2D currently.

AsyncCollider example:

use bevy::prelude::*;
use bevy_xpbd_3d::prelude::*;

fn setup(mut commands: Commands, mut assets: ResMut<AssetServer>) {
    // Spawn a cube with a convex hull collider generated from the mesh
    commands.spawn((
        AsyncCollider(ComputedCollider::ConvexHull),
        PbrBundle {
            mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
            ..default(),
        },
    ));
}

AsyncSceneCollider example:

use bevy::prelude::*;
use bevy_xpbd_3d::prelude::*;

fn setup(mut commands: Commands, mut assets: ResMut<AssetServer>) {
    let scene = SceneBundle {
        scene: assets.load("my_model.gltf#Scene0"),
        ..default()
    };

    // Spawn the scene and automatically generate triangle mesh colliders
    commands.spawn((
        scene.clone(),
        AsyncSceneCollider::new(Some(ComputedCollider::TriMesh)),
    ));

    // Specify configuration for specific meshes by name
    commands.spawn((
        scene.clone(),
        AsyncSceneCollider::new(Some(ComputedCollider::TriMesh))
            .with_shape_for_name("Tree", ComputedCollider::ConvexHull)
            .with_layers_for_name("Tree", CollisionLayers::from_bits(0b0010))
            .with_density_for_name("Tree", 2.5),
    ));

    // Only generate colliders for specific meshes by name
    commands.spawn((
        scene.clone(),
        AsyncSceneCollider::new(None)
            .with_shape_for_name("Tree".to_string(), Some(ComputedCollider::ConvexHull)),
    ));

    // Generate colliders for everything except specific meshes by name
    commands.spawn((
        scene,
        AsyncSceneCollider::new(ComputedCollider::TriMesh)
            .without_shape_for_name("Tree"),
    ));
}

---

Changes to methods

I also renamed and added some more methods to make things more consistent and simple. I removed _bevy from the names because this crate is already for Bevy so it's unnecessary to have the prefix.

Renamed

• trimesh_with_flags → trimesh_with_config
• convex_decomposition_with_params → convex_decomposition_with_config
• trimesh_from_bevy_mesh → trimesh_from_mesh
• trimesh_from_bevy_mesh_with_flags → trimesh_from_mesh_with_config
• convex_decomposition_from_bevy_mesh → convex_decomposition_from_mesh

Added

• convex_decomposition_from_mesh_with_config
• convex_hull_from_mesh