How can I remove the weird radial shadow at the intersection between my columns and the roof? thanks!
I’m afraid it’s not possible. The real-time skylight shadow effect is just an approximation, and it doesn’t look that good around long, narrow objects such as pillars.
The only way to fix this is to implement a different shadowing algorithm.
Switching to Raytraced or going to Render -> Render will do a “real” rendering which won’t have these issues.