Been working on the sun and sky a bit today. The sky still has a long way to go - right now it's just a clear blue sky at all times, but the lens flares for the sun have come a long way pretty quickly. They were a lot easier to do than I was expecting, which makes a pleasant change.
Here's my reference...
Obviously something as strong as this would be really distracting, so I went for something a little less strong.
The system essentially allows you to specify a material, distance and size for each flare, which slide around your screen based on where you're looking and the distance value. By incorporating the distance from source into the materials I was able to do things like fade them as the player looks away, and increase their size or strength when looking straight-on. This is best demonstrated with motion, but here's a couple of screens anyway.