glass bottle as two shells

I’ve been experimenting with a glass bottle render, based on a model I did several years ago in scanline

the bottle has an outer shell with a displacement map of a logo and an inner shell without - then it has a “liquid” filling (coloured semi transparent stuff)
Anyway I didnt get very far with the glass till I attached the inner and outer surfaces and added a cap between them

But that means both the inner and outer will be displaced which must add to render time - I’m sure I’ve read that applying a displacement to selected faces can leave visible map edges ?

I’m curious : does vray “prefer” to work with a closed solid when dealing with a glass mat?

Did you apply one and the same material to both surfaces (not simply two materials with the same parameters)?

Best regards,
Vlado

it was the same material..
the main reason I’m confused is that I did a little test with booleaned hemispheres to make a bowl shape - removing the top surface stops it looking like glass - but I suppose that is because light is bouncing internally and the light that enters from the top is adding significantly to the reality

the actual bottle has a metal lid so no light is entering from the top - and maybe that makes it harder to light with a “studio lighting” setup