I noticed about a month ago that inside faces with alpha now get rendered as black instead of being rendered alpha, unless the outside faces also have alpha. Until a few days ago I thought it was just a texture cache issue with a mirror object that I use that normally shows the avatar through an alpha texture. But it didn't go away after I cleared the texture cache, so I finally tested it with a hollowed prim. Today I discovered that the inside alpha is only rendered properly if the outside has alpha.
I made a test object so you can see if it's a viewer issue or not, but I didn't know if it's ok to send. You can make one like this:
1. Create a large cube and hollow to 95.
2. Set alpha of inside face to 100.
3. Set alpha of outside East face to 100.
4. Set alpha of outside West face to 100.
For me, that leaves the inside North and South faces as black, and the Inside East and West faces as invisible.
I'm using the latest Windows version, 1.26.22.55. I don't have any older versions from the last month to test with.