The term usually used for this is volumetric meshing.
If it is with little distorted cube-like elements, then more specifically it is called hexahedral meshing.
(the other common type being tetrahedral meshing).
Like with quads/triangles, hexahedral meshes are usually harder to generate for general shapes than tetrahedral ones.
If it is specifically for this single distorted box-like shape, the method shown by @HS_Kim looks good.
If you are looking for something to work with general shapes, then you’ll need a library.
For tetrahedral meshing there’s this plugin from @tom_svilans :
For hexahedral, I don’t know of anything available in Grasshopper. I think some commercial tools are available that work directly with Rhino, such as Moldex3D
, and Cheetah
, but not for free. If you don’t mind going out of Rhino to do this meshing there are many more options, though I think it’s still hard to find good ones for free (I believe there’s one in OpenFoam).