Background image change with fade effect

background-fade.txt

$(document).ready(function () {
    var index          = 1;
    var coverIndex     = 2;

    var imagePath      = "";
    var coverImagePath = "";
    var b              = false;

    setInterval(function () {
        index          = (index == 3 ?  1 : index + 1);
        coverIndex     = (coverIndex == 3 ? 1 : coverIndex + 1);
        imagePath      = '/images/agency/background/background-' + index + '.jpg';
        coverImagePath = '/images/agency/background/background-' + coverIndex + '.jpg';

        $.log(imagePath, coverImagePath);
        if (b) {
            b = false;
            $("#fullPage").animate({"opacity": 1}, 3000, function() {
                $("body").css({"background-image": 'url("' + imagePath + '")'});
            });
        } else {
            b = true;
            $("#fullPage").animate({"opacity": 0}, 3000, function(){
                $("#fullPage").css({"background-image": 'url("' + coverImagePath + '")'});
            });
        }
    }, 6000);
});

body {
    position: relative;
    background-image: url("/images/agency/background/background-1.jpg");
    background-repeat: no-repeat;
    background-size:   cover;
}

#fullPage {
    position: absolute;
    min-width: 100%;
    min-height: 100%;
    top: 0;
    left: 0;
    background-image: url("/images/agency/background/background-2.jpg");
    background-size: cover;
    opacity: 1;
}