> "jhu" <nomail@nomail> wrote:
>> "joe" <nomail@nomail> wrote:
>>> I've built a soda bottle with a bezier_spline lathe object.  It's clear glass,
>>> hollow and has a wall thickness.  To fill the bottle with soda I am creating
>>> another lathe object inside the bottle.  To prevent a coincident surface problem
>>> should I scale the soda larger to push the soda into the bottle wall?  Any
>>> better ways to fill a bottle with fluid?
>>
>> Here's what I usually do with such things. Make a lathe, subtract a slightly
>> smaller lathe to create a hollow object, then place a slightly smaller lathe
>> (just smaller than the difference) inside with appropriate media definitions. In
>> all, you should have 3 of the same lathes, just different sizes.
>
>
> With the liquid being slightly smaller than the cavity won't the air space
> between the liquid and the wall be visible in some slight way?
>
>
You won't see the gap itself if it's small enough.

BUT there will be extra reflections and highlights.
There will be broader total internal reflection from the glass object.
There will be total internal reflection from the liquid that should be 
totaly absent.
Those two effects are caused by the very small gap. There is no way to 
prevent those.
Making the liquid slightly larger also don't help as it just change the 
places where those problem will manifest themselves.

There will be reflection from the surfaces. Those can be reduced by 
tweaking the finishes of the glass and the liquid. It involve having a 
different finish only in the areas where the glass and liquid are in 
contact. Tricky but possible.



Alain

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