The light source only lights the faces which are oriented towards the light source.
Currently only one light source is allowed/taken into account by Wikitude3dEncoder.
If you want to avoid black, unlit faces, try specifying an ambient light source (usally a property of the scene) and adjust the faces' materials to use that ambient light source. That is, set an ambient light source color and the ambient color of the materials.
(What my colleague referred to in the last posting only applies to Blender.)
Note: If you use a point light source, the position of light source matters. Your light source is placed at the origin, that is, within the house.
about 6 years ago
We have made a fbx model of a garage and we have the issue with dark sides.
Would it be possible for you to show us how this can be achieved on the attached fbx model?