glass bottle as two shells

[glyph]

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?

[vlado]

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

Best regards,
Vlado

[glyph]

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