Filter wp_nav_menu()

I try to split my navigation into 3 single navigation bars (level 1, level 2 and level3+). Three because they’re separated over the site and they should only appear depending on the current page.

-0-------1--------2-------3+- level/depth
Home
 |
 |\___ Lobby
 |
 |\___ Projects
 |       |\___ Project A
 |       |       |\___ Review
 |       |       |\___ Comments
 |       |       \____ Download
 |       \____ Project B
 |               |\___ Review
 |               |\___ Comments
 |               \____ Download
 |\___ Blog
 |
 \____ About
         |\___ Legal
         \____ Contact

The first navbar containing the level 1 is always visible. The second navbar (level 2) only when im currently on the corresponding parent page. The same goes for the third navbar (level 3+, plus because this navbar will also contain sub pages and subsub pages … of level 3).

In short: I want to display all the parent menus in their navbars and only the direct children of the current page.

What I tried:

function my_nav_menu( $args = array() )
{
    $echo = isset( $args['echo'] ) ? (bool)( $args['echo'] ) : true;
    $args['echo'] = false;

    add_filter( 'wp_get_nav_menu_items' , 'my_nav_menu_filter' , 666 , 3 );

    $menu = wp_nav_menu( $args );

    remove_filter( 'wp_nav_menu_objects' , 'my_nav_menu_filter' , 666 );

    if( $echo )
        echo $menu;
    else
        return $menu;
}

function my_nav_menu_filter( $items , $menu , $args )
{
    //var_dump( $args );

    $navLevel = isset( $args['navlevel'] ) ? (int)( $args['navlevel'] ) : 0;

    //echo 'navlevel=" . $args["navlevel'] . ' | ' . $navLevel;

    if( $navLevel == 1 )
    {
        foreach( $items as $key => $item )
        {
            if( $item->menu_item_parent != 0 )
                unset( $items[$key] );
        }
    }
    else if( $navLevel == 2 )
    {
        foreach( $items as $key => $item )
        {
            if( $item->menu_item_parent != 0 )
            {
                $page = get_page( $item->menu_item_parent );

                if( $page->menu_item_parent == 0 )
                    continue;
            }

            unset( $items[$key] );
        }
    }
    else if( $navLevel == 3 )
    {
        foreach( $items as $key => $item )
        {
            if( $item->menu_item_parent != 0 )
            {
                $page = get_page( $item->menu_item_parent );

                if( $page->menu_item_parent != 0 )
                    continue;
            }

            unset( $items[$key] );
        }
    }
    else
    {
        //var_dump( $items );
    }

    return $items;
}

Calling this in my header.php:
<?php my_nav_menu( array( 'echo' => false , 'navlevel' => 1 ) ); ?>

However $args is set to the default values and my custom entry navlevel isnt shown in the filter.

How can I split my navbar as described?
How do I set my custom $args-entry?

I think I got the answer:

function my_nav_menu( $args = array() )
{
    $echo = isset( $args['echo'] ) ? (bool)( $args['echo'] ) : true;

    $args['echo'] = false;

    add_filter( 'wp_nav_menu_objects' , 'my_filter_nav_menu' , 100 , 2 );

    $menu = wp_nav_menu( $args );

    remove_filter( 'wp_nav_menu_objects' , 'my_filter_nav_menu' , 100, 2 );

    if( $echo )
        echo $menu;
    else
        return $menu;
}

This does the trick: lets me alter the menuitems and custom args are still available.
I accidentally hooked the filter into wp_get_nav_menu_items instead of wp_nav_menu_objects.
I still having problems with the filtering, however these are probably some logical bugs..

EDIT: i’ll solved my problem by combining navbar level 2 and navbar level 3+ into one and separating them with css

heres the current php part:

function serthy_filter_nav_menu( $items , $args )
{
    $argArray = (array)( $args );

    if( isset( $argArray['toplevel'] ) )
    {
        foreach( $items as $key => $item )
        {
            if( $item->menu_item_parent != 0 )
                unset( $items[$key] );
        }

        return $items;
    }

    global $post;

    $arr = array();

    foreach( $items as $key => $item )
    {
        $parentIDs = get_post_ancestors( $item->ID );

        foreach( $parentIDs as $i => $parentID )
        {
            if( $parentID == $post->ID )
            {
                array_push( $arr , $item );

                break;
            }
        }
    }

    return $arr;
}