Subtle bug in planetary ring shadows

[smcameron]

Where the ring shadows intersect the terminator, there's a hard edge that shouldn't be there. It's a little hard to see, but in the right circumstances it shows up. In the first picture below for example, the crater that's slightly lit up beyond the terminator should be shadowed by the rings, but it isn't, and the ring shadow hard stops at the terminator.

Some pics showing the effect:

It's a pretty minor thing, so not sure I'll bother to fix it (certainly not right away), but want to record its existence.