phaser/v3/src/math/easing/Elastic.js at 101e4f5be55adee6aa8215eb875fbf130d2d3aaa · ITCSsDeveloper/phaser · GitHub

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function In (v, amplitude, period)
{
    if (amplitude === undefined) { amplitude = 0.1; }
    if (period === undefined) { period = 0.1; }

    if (v === 0)
    {
        return 0;
    }
    else if (v === 1)
    {
        return 1;
    }
    else
    {
        var s = period / 4;

        if (amplitude < 1)
        {
            amplitude = 1;
        }
        else
        {
            s = period * Math.asin(1 / amplitude) / (2 * Math.PI);
        }

        return -(amplitude * Math.pow(2, 10 * (v -= 1)) * Math.sin((v - s) * (2 * Math.PI) / period));
    }
}

function Out (v, amplitude, period)
{
    if (amplitude === undefined) { amplitude = 0.1; }
    if (period === undefined) { period = 0.1; }

    if (v === 0)
    {
        return 0;
    }
    else if (v === 1)
    {
        return 1;
    }
    else
    {
        var s = period / 4;

        if (amplitude < 1)
        {
            amplitude = 1;
        }
        else
        {
            s = period * Math.asin(1 / amplitude) / (2 * Math.PI);
        }

        return (amplitude * Math.pow(2, -10 * v) * Math.sin((v - s) * (2 * Math.PI) / period) + 1);
    }
}

function InOut (v, amplitude, period)
{
    if (amplitude === undefined) { amplitude = 0.1; }
    if (period === undefined) { period = 0.1; }

    if (v === 0)
    {
        return 0;
    }
    else if (v === 1)
    {
        return 1;
    }
    else
    {
        var s = period / 4;

        if (amplitude < 1)
        {
            amplitude = 1;
        }
        else
        {
            s = period * Math.asin(1 / amplitude) / (2 * Math.PI);
        }

        if ((v *= 2) < 1)
        {
            return -0.5 * (amplitude * Math.pow(2, 10 * (v -= 1)) * Math.sin((v - s) * (2 * Math.PI) / period));
        }
        else
        {
            return amplitude * Math.pow(2, -10 * (v -= 1)) * Math.sin((v - s) * (2 * Math.PI) / period) * 0.5 + 1;
        }
    }
}

module.exports = {

    In: In,
    Out: Out,
    InOut: InOut

};