The lightmap space needed for a scene depends on the total area of the objects in the scene, even a small number of large triangles can have large total area.
It looks like you have correctly reduced the resolution for large external objects that don’t need detailed shadows using the
Custom lightmap resolution setting. This message says that even after your reduction, the scene still couldn’t be fit into 2 lightmaps and the resoultion was reduced further by 6%. This isn’t a large reduction and shouldn’t affect the quality much . You can check the final resolution used in the
Auto lightmap resolution property.
As you can see, for important interior objects, the resolution was automatically reduced from
70, which isn’t a big difference, but if you would like to avoid this reduction you can further decrease the resolution for the largest external objects.
The main problem seems to be too dark interior, which is not related to the lightmap resolution. To improve this you could:
- Decrease the windows opacity for the time of baking to let more sky light inside. After the baking you can increase the opacity back to
- Increase the sky strength (for example to
4) and use the
Camera volumes feature in the
Viewer tab to reduce exposure when the camera enters the balcony to avoid showing overexposed exterior.