Below is a double-sided material in Rhino8 and in Rhino9. It’s the same material. In Rhino9, the transparency isn’t working. The cool thing about double-side transparent materials is you can see IN but not THROUGH the object, which is exactly the effect I was going for. It works in Rhino7 and Rhino8, but not Rhino9.
The actual RMTL file is attached.
Gem - Stylized - Sapphire.rmtl (20.2 KB)
system_info_r9.txt (2.9 KB)