There are dozens of these images at RDNA - I posted them so you would know how much light would pass through various thickness of a solid object.

This particular one is marble, scale=.2.

The numbers on each box tell you the thickness in inches.

Your lamp shade should be set up very easily, but if it is one-sided you will not get maximum realism.

You must understand that one-sided props are truly a nono when trying to treat them as containing a volume of various thickness containing a transmitting medium.

x-post I see you do understand. Nevertheless what it means is you will have to play with values. It does not mean it won't work.

Look at my shower curtain draped over Andy. That is one-sided.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)