title: navigation tilemaps without placing walkable tiles manually
body: <p>I have a tilemap in godot, but all tiles are obstacles and provide collision. Only cells without any tile are walkable. I'm now trying to add navigation via Navigation2D node. As far as I see there is no way to tell it "everything is walkable, but not where these tiles are" (all one can say is "this part of the tile is walkable", but in my current setup there is no tile at the walkable space).</p>
  
  <p>As a workaround I tried to set every cell with no tile to a "dummy tile" which is fully walkable with the following code:</p>
  
  <pre><code>func _ready():
      for x in size.x:
          for y in size.y:
              var cell = get_cell(x, y)
              if cell == -1:
                  set_cell(x, y, WALKABLE)
  </code></pre>
  
  <p>But the Navigation2D node does not recognize these tiles. If I place the <code>WALKABLE</code> tile manually, everything works as expected.</p>
  
  <p>I think I might be hitting <a href="https://github.com/godotengine/godot/issues/11077" rel="nofollow noreferrer">this issue</a>, and need to call <code>update_dirty_quadrants()</code> but this does not fix the problem.</p>
  
  <p>I tried this with the versions 3.0.6stable, 3.1Alpha2 and a recent commit 9a8569d (<a href="https://ifiregames.itch.io/stern-flowers-chibifire-com-godot-engine" rel="nofollow noreferrer">provided by godotwild</a>), and the result was always the same.</p>
  
  <p>Is there anyway to get navigation with tilemaps working, without placing every tile beforehand manually?</p>