Objective

As we all know, Collider is not Reflect. This is a bit of a problem for people wanting to load collider shapes from code-external sources. Notably, people using @kaosat-dev 's excellent Blender-GLTF workflow as an editor need to setup their own Reflect version of Collider all the time, usually something like this:

#[derive(Debug, Component, Reflect)
#[reflect(Component)]
enum Collider {
  Cuboid {...},
  Sphere {...},
  Trimesh,
  ...
}

and then attach XPBD colliders to entities holding the above fake collider.
I've been thinking about opening a PR on the Blender workflow to do this automatically based on a cargo feature, but then I thought that maybe this would be better in XPBD / Avian proper so that other reflect-heavy workflows may profit from it as well. I'm thinking about scene structures, embedding colliders in BSN and future Bevy editor prototypes.

Solution

My approach is to extend ComputedCollider to cover all variants of creating a collider. Some of these require a Mesh, some don't. When going through AsyncColliders, I can see if the specified creation method needs a Mesh. If so, the entity that the AsyncCollider is on must also hold a Handle

Changelog

• Reworked deferred / "async" collider initialization. Renamed most involved types.
  • ComputedCollider and AsyncCollider have been combined into ColliderConstructor and support all possible collider shapes except compounds.
    • ColliderConstructor is Reflect, Serialize and Deserialize. You can use it to statically configure your colliders when loading them from code external sources such as save files or serialized level definitions.
    • ColliderConstructor supports creating primitive shapes, so it does not need to be placed on an entity holding a mesh.
    • ColliderConstructor can be used in 2D when not using computed shapes
  • AsyncSceneCollider is now called ColliderConstructorHierarchy and no longer requires being placed on a Scene. It will generally generate a collider for all available descendants.
    • Changes to ColliderConstructor also apply here
    • If the new default feature bevy_scene is enabled, placing ColliderConstructorHierarchy on a Scene will still wait until the scene is loaded
    • When the desired collider shape should be created from a mesh, only descendants holding a mesh will receive a collider
    • This type is now especially useful for generating colliders on objects defined with the Blender to Bevy workflow
    • ColliderConstructorHierarchy::new now takes an impl Into<Option> instead of an Option, so you can drop the Some from your calls if you want: AsyncSceneCollider::new(Some(Foo)) becomes ColliderConstructorHierarchy::new(Foo)
    • ColliderConstructorHierarchy can be used in 2D when not using computed shapes
  • bevy_scene can now be feature gated off while still using deferred colliders
• bevy_gltf is no longer pulled in

Migration Guide

• Remove feature async-collider. If you need to use computed shapes, use the feature collider-from-mesh. If you depend on ColliderConstructorHierarchy waiting for a scene to load, use the feature bevy_scene
• Remove AsyncCollider and use ColliderConstructor directly
• Rename AsyncSceneCollider to ColliderConstructorHierarchy
  • Rename AsyncSceneCollider::default_shape to ColliderConstructorHierarchy::default_constructor
  • Rename AsyncSceneCollider::meshes_by_name to ColliderConstructorHierarchy::config
  • Rename AsyncSceneCollider::with_shape_for_name to ColliderConstructorHierarchy::with_constructor_for_name
  • Rename AsyncSceneCollider::without_shape_for_name to ColliderConstructorHierarchy::without_constructor_for_name
• Rename AsyncSceneColliderData to ColliderConstructorHierarchyConfig
  • Rename AsyncSceneColliderData::shape to ColliderConstructorHierarchyConfig::constructor
• Rename ComputedCollider to ColliderConstructor.
  • Rename ComputedCollider::TriMesh to ColliderConstructor::TrimeshFromMesh
  • Rename ComputedCollider::TriMeshWithFlags to ColliderConstructor::TrimeshFromMeshWithConfig
  • Rename ComputedCollider::ConvexHull to ColliderConstructor::ConvexHullFromMesh
  • Rename ComputedCollider::ConvexDecomposition to ColliderConstructor::ConvexDecompositionFromMeshWithConfig
• Rename VHACDParameters to VhacdParameters
• Rename Collider::halfspace to Collider::half_space

Linked Issues

• Indirectly resolves Sensor not working on AsyncSceneCollider #309 by verifying that something like that is not really possible in the current version
• Resolves Remove bevy/bevy_gltf dependency from async-collider #306