These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.23 s (backtrack: 0/20).


The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by media-gfx/hugin-2025.0.1::gentoo
# required by =media-gfx/hugin-2025.0.1 (argument)
>=media-libs/vigra-1.12.2 openexr

!!! The ebuild selected to satisfy ">=sci-libs/hdf5-1.8.0:=[mpi=]" has unmet requirements.
- sci-libs/hdf5-2.2.0::gentoo USE="hl threads zlib -cxx -debug -fortran -mpi -szip -test -unsupported"

  The following REQUIRED_USE flag constraints are unsatisfied:
    !unsupported? ( threads? ( !hl ) )

  The above constraints are a subset of the following complete expression:
    !unsupported? ( at-most-one-of ( cxx mpi ) threads? ( !cxx !mpi !fortran !hl ) )

(dependency required by "media-libs/vigra-1.12.2::gentoo" [ebuild])
(dependency required by "media-gfx/hugin-2025.0.1::gentoo" [ebuild])
(dependency required by "=media-gfx/hugin-2025.0.1" [argument])