function get_render_rd_url (bounds) {
	var res = this.map.getResolution();
	var x = Math.round ((bounds.left - this.maxExtent.left) / (res * this.tileSize.w));
	var y = Math.round ((this.maxExtent.top - bounds.top) / (res * this.tileSize.h));
	var z = this.map.getZoom();
	var path = z + "/" + x + "/" + y + "." + this.type;
	var url = this.url;
	if (url instanceof Array) {
		url = this.selectUrl(path, url);
	}
	return url + path;
}

function get_render_world_url (bounds) {
	var res = this.map.getResolution();
	var x = Math.round((bounds.left - this.maxExtent.left) / (res * this.tileSize.w));
	var y = Math.round((this.maxExtent.top - bounds.top) / (res * this.tileSize.h));
	var z = this.map.getZoom();
	var limit = Math.pow(2, z);
	if (y < 0 || y >= limit) {
		return "http://openstreetmap.org/openlayers/img/404.png";
	} else {
		x = ((x % limit) + limit) % limit;
		var url = this.url;
		var path = z + "/" + x + "/" + y + ".png";
		if (url instanceof Array) {
			url = this.selectUrl(path, url);
		}
		return url + path;
        }
}