[rgl]

var setOpacity = function() {
  var op, to;
  return function () {
    if( to )
      clearTimeout( to );
    to = null;
    var id = document.getElementById('big');
    op = -1;
    (function _() {
      id.style.opacity = ++op/10;
      if( op < 10 )
        to = setTimeout( _, 100 );
      else
        to = null;
    })();
  }
}();