how i calculate how much liters of liquid contain in bottel ?
just an idea (I don't know squat about NX...)
in Inventor I just:
1) add a new surface to define the top of fluid level (must be bigger than the cross-section of the bottle)
2) copy inside surface of bottle (one blended surface/quilt)
3) switch off solid
4) then I use "sculpt"-tool to merge the 2 surfaces into a NEW solid
this new solid you can get properties from.
if you can't do something like 4) above; the 2 surfaces should intersect each other. use the one to split the other one (... both surfaces split). now patch the closed surfaces to form new solid.
I hope this helps :)