Backface Culling
Why faces vanish when seen from behind
Also known as: Back face culling · Back-face culling · Single-sided faces · Cull mode · Render Face
Quick answer
Backface culling is a rendering optimization where the GPU skips faces that point away from the camera, so a single-sided plane or wall becomes invisible when you view its back. A face's front is decided by its normal, so a mesh with flipped normals shows its inside and hides its outside. To see the back, enable the engine's two-sided or render-both-faces option, or fix the normals if they point the wrong way.
How to fix it
In Unreal Engine tick Two Sided on the material. In Blender, the Backface Culling checkbox in the material settings controls whether back faces are hidden in the viewport and render; turn it off to see them. In Unity URP Lit materials, set Render Face to Both. Culling is on for a reason, since it saves shading work on closed, solid meshes, so leave it on and give thin objects real thickness whenever you can.
