bevy_fabrik 0.2.1

IK solver for Bevy using FABRIK algorithm
Documentation 
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//! [FABRIK] inverse kinematics implementation for [Bevy].
//!
//! [FABRIK]: https://www.andreasaristidou.com/FABRIK.html
//! [Bevy]: https://bevyengine.org

mod chain;
mod constraint;
mod util;

use bevy::prelude::*;
use bevy::transform::TransformSystem;

pub use crate::chain::IkChain;
pub use crate::constraint::{SwingConstraint, TwistConstraint};

fn ik_solve(
    mut chain_query: Query<(Entity, &mut IkChain)>,
    mut constraint_query: Query<(Option<&SwingConstraint>, Option<&TwistConstraint>)>,
    mut transform_query: Query<(Option<&Parent>, &mut Transform, &GlobalTransform)>,
) {
    // TODO: Multi-chain structures
    for (entity, chain) in chain_query.iter_mut() {
        if let Err(e) = chain.solve(&entity, &mut constraint_query, &mut transform_query) {
            warn!("Failed to solve IK chain: {:?}", e);
        }
    }
}

/// Set enum for the systems relating to inverse kinematics
#[derive(Debug, Hash, PartialEq, Eq, Clone, SystemSet)]
pub enum IkSystem {
    /// Solves inverse kinematics chains
    Solve,
}

/// [`Plugin`] for inverse kinematics. Needs to be added to the [`App`] for
/// [`IkChain`] components to solve and apply transforms.
pub struct InverseKinematicsPlugin;

impl Plugin for InverseKinematicsPlugin {
    #[rustfmt::skip]
    fn build(&self, app: &mut App) {
        app.register_type::<IkChain>()
            .register_type::<SwingConstraint>()
            .register_type::<TwistConstraint>()
            .add_systems(PostUpdate, (
                ik_solve,
            ).after(TransformSystem::TransformPropagate).in_set(IkSystem::Solve)
        );
    }
}