Blender-created meshes appear transparent when viewed from the inside.

Question

I have a custom torus-based environment I imported from a Collada file (created in Blender) that whenever it is viewed from the inside, appears transparent from any camera perspective, regardless of if a game is running or from the editor.

I'm not clear on what the cause is here with this mesh -- at first I made sure it wouldn't occur again with I "Triangulate" the mesh, to the same results. The same behavior exhibits itself when I import from an OBJ file (seen in the distance on the first photo).

I'm sure that i'm missing a step in the process, any ideas on what I can do to remedy it?

The original Blend file and DAE/OBJs can be viewed/downloaded here.

Answer 1

By default Godot culls back-facing polygons which leads to the walls disappearing when you're inside the mesh. To fix this, flip the normals of the mesh in Blender or set the Godot material to "Double Sided". Using the "Flip Faces" option when importing the mesh fixes the disappearing walls but the lighting appears wrong.