I did see a procedural 'fake' glass shader product that claimed to render very fast, just a couple of days ago. (I wasn't sure what they meant by 'fake'... isn't it all? Anyway, it looked convincing.)

I'd have to check my browser history when I get home this evening to find out where it was. I don't think it was here at Rendo.... it might have been RDNA.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)