This is pretty much the same as the last version, except for  a few bugfixes and a test for a "God-Rays" effect. Pity it is rather slow and still far from properly implemented, but I thought I show this, let me know what you think.

The effect is still too much center-based, making it look like the sun is rotating with the camera, but the idea was more like rays from a diffuse sky that cut a shady mist. Maybe a more orthographic CameraFocus can spread the actual "light center" of the effect more evenly across the entire visible sky. We'll see.

Turn the effect on and off by "r".