Here is a comparison of MOI v5 with RHINO
MOI v5 the volume is not correct

Hi Brian, can you please post the .3dm model file or e-mail it to me at moi@moi3d.com ?

- Michael

Here is an example of the model

Hi Brian, looks like a bug. Here is a version that keeps the lines and arcs separate and that seems to work better.

- Michael

and what exactly are the problems? because such an incorrect calculation occurs quite often

Hi Brian, I'm still examining the cause but it looks like a bug in the geometry library's integration mechanism.

If you have other volume calculation cases that fail please send the .3dm files for them to me at moi@moi3d.com so I can see if they are the same problem or if they're different problems.

- Michael