bevy_fabrik 0.1.0

IK solver for Bevy using FABRIK algorithm
Documentation 
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use bevy::prelude::*;

pub trait QuatExt {
    fn decompose(&self, dir: Vec3) -> (Quat, Quat);
    fn constrain(rotation: Quat, angle: f32) -> Quat;
}

impl QuatExt for Quat {
    fn decompose(&self, dir: Vec3) -> (Quat, Quat) {
        let projected = self.xyz().project_onto(dir);
    
        let twist = Quat::from_xyzw(projected.x, projected.y, projected.z, self.w).normalize();
        let swing = *self * twist.inverse();
    
        (twist, swing)
    }

    fn constrain(rotation: Quat, angle: f32) -> Quat {
        let magnitude = f32::sin(0.5 * angle);
        let sqr_magnitude = magnitude * magnitude;
    
        let mut vector = rotation.xyz();
    
        if vector.length_squared() > sqr_magnitude {
            vector = vector.normalize() * magnitude;
        
            return Quat::from_xyzw(
                vector.x,
                vector.y,
                vector.z,
                f32::sqrt(1.0 - sqr_magnitude) * f32::signum(rotation.w)
            );
        }
        rotation
    }
}