Function volume_properties 

pub fn volume_properties(
    model: &Model,
    shape: &Shape,
    deflection: Deflection,
    tol: Tolerances,
) -> OgeomResult<MassProperties>

The volume a shape encloses, and how it is distributed.

Each shell of a solid with several is weighed facing out of the solid’s material, as a probe off its faces finds: a void whose faces all point into the material (turned inside out as a whole, which no edge between its faces shows) is still taken away, not added. A face whose flag points into the material, against the neighbours it shares edges with, is counted turned back the same way.

Errors

As surface_properties, plus OgeomError::Construction if the boundary is not closed, or is wound inward so that the volume comes out negative. Both mean the answer would be meaningless rather than merely inaccurate: the divergence theorem needs a closed, outward-oriented boundary, and without one the sum is a number with no interpretation.