Cal3D is a skeletal based 3D character animation library written in C++
in a way that is both platform-independent and graphics API-independent.
It was originally designed to be used in a 3D client for Worldforge, but
evolved into a stand-alone product which can be used in many different
kinds of projects.

Cal3D's essentials can be boiled down to 2 parts: the C++ library and
the exporter. The exporter is what you would use to take your characters
(built in a 3D modeling package) and create the Cal3D-format files that
the library knows how to load. The exporters are actually plug-ins for
3D modeling packages. This allows 3D artists to use the modeling tools
that they're already comfortable with.

The C++ library is what you would actually use in your application,
whether it's a game or a VR application. The library provides methods to
load your exported files, build characters, run animations, and access
the data necessary to render them with 3D graphics.