HaxePunk/HaxePunk

package haxepunk.tweens.motion;

import haxepunk.utils.Ease.EaseFunction;

/**
 * Determines motion along a cubic curve.
 */
class CubicMotion extends Motion
{
    /**
     * Starts moving along the curve.
     * @param    fromX        X start.
     * @param    fromY        Y start.
     * @param    aX            First control x.
     * @param    aY            First control y.
     * @param    bX            Second control x.
     * @param    bY            Second control y.
     * @param    toX            X finish.
     * @param    toY            Y finish.
     * @param    duration    Duration of the movement.
     * @param    ease        Optional easer function.
     */
    public function setMotion(fromX:Float, fromY:Float, aX:Float, aY:Float, bX:Float, bY:Float, toX:Float, toY:Float, duration:Float, ?ease:EaseFunction)
    {
        x = _fromX = fromX;
        y = _fromY = fromY;
        _aX = aX;
        _aY = aY;
        _bX = bX;
        _bY = bY;
        _toX = toX;
        _toY = toY;
        _target = duration;
        _ease = ease;
        start();
    }

    /** @private Updates the Tween. */
    @:dox(hide)
    override function updateInternal()
    {
        x = _t * _t * _t * (_toX + 3 * (_aX - _bX) - _fromX) + 3 * _t * _t * (_fromX - 2 * _aX + _bX) + 3 * _t * (_aX - _fromX) + _fromX;
        y = _t * _t * _t * (_toY + 3 * (_aY - _bY) - _fromY) + 3 * _t * _t * (_fromY - 2 * _aY + _bY) + 3 * _t * (_aY - _fromY) + _fromY;
    }

    // Curve information.
    var _fromX:Float = 0;
    var _fromY:Float = 0;
    var _toX:Float = 0;
    var _toY:Float = 0;
    var _aX:Float = 0;
    var _aY:Float = 0;
    var _bX:Float = 0;
    var _bY:Float = 0;
}