August 28, 2013, 01:36:11 am
Which Lumion are you using?
For the corners between walls and ceilings, that's the Ambient shadow (sometimes known as SSAO), and is controlled by the three Ambient sliders in the Shadow Effect.
The amount of grey over white materials is the result of the shadows for the interior, it's affected by the amount of sun light, ambient light, number of lights added to the interior, and any GI used.
Interior ceilings do tend be a bit dark, and a little emissive on the material will whiten it, as a quick way to account for some more ambient light.
If needed you can also add some further light to interiors (excluding use of GI) by adding one or two Fill Lights.