title: difficulty in add navigation mesh
body: <p>I have a ui image in canvas in 3D environment .
  after add a <code>navmesh</code> component  and run  unity,my image  becomes vertical.</p>
  
  <p><a href="https://i.stack.imgur.com/JHpNk.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/JHpNk.png" alt="before run unity "></a></p>
  
  <p><a href="https://i.stack.imgur.com/buKsK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/buKsK.png" alt="after run unity"></a></p>
  
  <p>I don't know .please help</p>