FX

package whiteout;

import javafx.animation.SimpleInterpolator;
import java.lang.Math;


/* This is the actual interpolator class which implements
 * the standard spring equation.
 * It can be configured using the public-init vars
 * at the top, but reasonable defaults are provided.
 * */

public class SpringInterpolator extends SimpleInterpolator {
    // the amplitude of the wave
    // controls how far out the object can go from it's final stopping point.
    public-init var amplitude:Number = 1.0;

    // determines the weight of the object
    // makes the wave motion go longer and farther
    public-init var mass:Number = 0.058;

    // the stiffness of the wave motion / spring
    // makes the motion shorter and more snappy
    public-init var stiffness:Number = 12.0;

    // makes the wave motion be out of phase, so that the object
    // doesn't end up on the final resting spot.
    // this variable is usually never changed
    public-init var phase:Number = 0.0;

    // if this should do a normal spring or a bounce motion
    public-init var bounce:Boolean = false;


    def pulsation = Math.sqrt(stiffness / mass);

    // the actual spring equation
    override public function curve(t: Number) : Number {
        def t2 = -Math.cos(pulsation * t + phase+Math.PI) * (1 - t) * amplitude ;

        // use the absolute value of the distance from the end point
        // if doing a bounce
        if (bounce) 1 - Math.abs(t2) else 1 - t2;
    }
}