curve.rs

fn curve(ms: Ms, p: [Vec2<f32>; 4]) -> State {
    time_func(Timer::new(ms), box move |sprite, timer| -> Option<State> {
        // Cubic Bézier curves
        use num::Float;

        if timer.is_out() { return Some (Static) }

        let t = timer.ratio();
        let r = 1.0 - t;

        let a =               r.powi(3);
        let b = 3.0*t        *r.powi(2);
        let c = 3.0*t.powi(2)*r        ;
        let d =     t.powi(3)          ;

        sprite.transform.position = p[0] * a + p[1] * b + p[2] * c + p[3] * d;
        return None;
    })
}