title: Unity URP weird looking lightmap issue
body: <p>if i apply lightmap i get this result :</p>
  <p><a href="https://i.stack.imgur.com/EaJRu.png" rel="nofollow noreferrer">https://i.stack.imgur.com/EaJRu.png</a></p>
  <p>Lightmap Preview :</p>
  <p><a href="https://i.stack.imgur.com/JUmZ1.png" rel="nofollow noreferrer">https://i.stack.imgur.com/JUmZ1.png</a></p>
  <p>Lightning Settings :</p>
  <p><a href="https://i.stack.imgur.com/OGjOd.png" rel="nofollow noreferrer">https://i.stack.imgur.com/OGjOd.png</a></p>
  <p>I don't know if it's related to the material, but I'm putting the screenshot here anyway :</p>
  <p><a href="https://i.stack.imgur.com/r1cgz.png" rel="nofollow noreferrer">https://i.stack.imgur.com/r1cgz.png</a></p>
  <p>I'm also using Unity version 2020.3.12f1 and URP v10.5.</p>