one side shadow

theres no shadow from top side,i’ve checked " shadow two sided",problem remained,what can i do to solved it,thanks.

This can be solved in two ways:

  1. Include 2 sides in the material, but the more meshes with such material on the scene, the greater the load on the video card.
  2. Make the wall thickness in the model at least 10 cm (the most optimal option)

Hello, it’s a little hard to tell from the screenshot, but I think you need to cap the top of the mesh. It won’t make a shadow if there is no geometry there.