The current functionality of Pro/E to find internal volume is abyssmal. Users are forced to subtract parts and assemblies from a solid and find the resulting volume. The process breaks down even further if the components themselves have internal volumes, such as tanks or tubes within a larger assembly. For very large assemblies, the process does not work at all because of limitations of the shrinkwrap utility.
Please add a function to find the internal volume of a body using a more elegant solution, such as ray tracing with multiple light sources, acoustic waves, etc.