I solved and tell you how to compare with you:
- selection of internal surfaces model
-topped openings with fill
- at this point I can use volume analysis
It is simple when simple piece, you select the interior surfaces one by one, but when complex part with difficulty, sometimes access to some internal surface, like a foundry model with many cavities, it becomes laborious.
There is a fast way to select the internal surfaces: "limit and departure surfaces"
