Skylights are excellent for interiors! Just make sure they are set to static, not stationary. When they try to dynamically emit light (stationary and movable) you end up with a blue world because it can’t be accurate about occlusion. So set everything static, and turn up your Lightmass Settings within your World Settings. Static Lighting Level Scale = 0.3 and Indirect Lighting Quality = 4. You should see an improvement if your walls are set up nicely so there isn’t any leaking.
Actually, both static and stationary sky lights correctly support precomputed static shadows. There’s a subtle difference between how static and stationary sky lights work, but it usually doesn’t matter. If you’re curious, I believe there are only two differences – with stationary skylights, the color and intensity of the direct component can be altered in real time (as always, bounce light cannot be recomputed at run-time). Stationary sky lights also use some kind of bent normal technique on the direct component to help points where meshes touch each other “match” better. For some reason I can’t find this in the documentation, though. Static skylights don’t support this as they don’t distinguish the direct and indirect components separately.
If you’re already using either a static or stationary sky light and still getting “ambient” light and no accurate shadows, make sure that the interior geometry is actually marked as static and that the lighting is actually being built successfully.
As far as movable sky lights go, it’s impossible to get perfect shading, but in certain scenarios distance field ambient occlusion can do a fairly reasonable approximation.
Finally, there’s an obscure undocumented feature that might be able to help, called “diffuse from captures” – this is supposed to allow diffuse lighting to be based off of the irradiance maps used for reflection captures. I’ve heard that it doesn’t work properly in any recent engine versions, as it hasn’t been maintained for a long time. I doubt it’ll help at all, but it’s an obscure enough thing that I figure it’s worth mentioning in case someone ever finds a use for it (and gets it to work).
here is the update shot of my file,now lighting looks a bit okay but some object is not casting shaddow. if you see the attachment, opposite wall looks blue , confused…