As of 5.3 b1, I get a tooltip telling me that casting shadows is only possible from opaque materials, why? That's kind of an arbitrary restriction to introduce. I tested and the real requirement is depth write must be enabled. I hope this restriction is reverted, it's not very unity-like, so what if I wanna cast shadows but not receive them with self-shadowing? It looks good in my project, and I liked it. My main reason for sticking with unity is that it doesn't make assumptions on how I wanna use it.