When creating a large interior space with walls and a ceiling, it is recommended to setup the face normals in such a way that you will be able to see through them when viewed from outside the mesh.
An example can be seen below:
To achieve this in Blender, you need to make sure the roof and walls are planes, instead of boxes, otherwise this technique will not work.
Normals tell the renderer which direction a material or texture should be visible from.
In the image above, the vertex and face normals are pointing outwards, which means that the sphere will be viewable from the outside. However, if a user were to go inside, the sphere would disappear. For room models, this is usually the opposite of what we want, so we would need to flip the normals around.
To do this:
- In Blender, with your object selected, select "Edit Mode"
- Select Mesh > Normals > Flip Normals
Now you will be able to see inside your object while not having your view obstructed from the outside.