Why are my shadows so grainy?

[Myster Stranger]

I created a small test room involving simulated daylight using spot lights, but the shadows they produce are extremely grainy, even on the highest settings. In-game, the grains are actually persistent, and follow where you look. Not sure what I'm doing wrong.

http://i.imgur.com/W7xI9an.png

I'd really appreciate some guidance. Thanks!

I'd recommend splitting the job up, if I remember correctly, each spotlight has a predefined shadow resolution, a resolution set more for a single flickering spotlight with a narrow FOV, not the entirety of the sun. I'm actually creating a map at the moment that had a similar problem initially, in which a massive metal complex has light provided by a single spotlight, but I replaced the one with 8, all in the same location, each with an narrow FOV and massive radius, all slightly off from each other. The shadows this setup has provided are pretty great, with no noticeable performance hit, so see if that suits your needs.