i am familar with unigraphics 8 And solid work 20112
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 :)
Actually i want technical way how to define at specific point this much liters of fluid contain like marking on Medicine bottle or container.And thanks Mr. Wilhelm for your suggestion
Try to make hallow surface into solid body & check it mass by applying material. & Give water density at room temperature or temperature of running.