UVPackmaster 2 is an efficient and fully-featured UV packing engine available as a command line tool. It is probably the most efficient UV packer out there in terms of packing on CPU but it also provides a Cuda accelerated variant of the algorithm. When running on a GPU it significantly outperforms all other packers available.
Note that UVPackmaster doesn’t only mean high performance – it also provides a lot of sophisticated features greatly simplifying your UV packing workflow.
The engine can be used together with Blender (2.8 - 2.9) with the UVPackmaster add-on installed.