the shades on the roof are a bit confuse...where's suposed to be the sun? left? right? top?
look. if the roof is round, it would have a side darkened and a side lightened, not the same luminosity along the whole surface. Think of that. Put the lightsource in a virtual position and keep it there, remember where the light comes from and where the shadows are projected to.
This can look much better. Try it and do it
