The s2geometry package, written in C++, is the engine behind Google
Earth, designed in the first place to retrieve geospatial information
quickly but having basic support for discretized spherical geometry,
so that efficient rasterized images at the desired resolution can be
constructed quickly . An open source version, "not an official
Google product", is available from GitHub. There's a Python 2.7
binding made with SWIG. Now SWIG is "designed to work with Lua 5.0.x
and Lua 5.1.x" but "should work with later versions of Lua". Not being
a fan of SWIG-generated bindings (they give you that authentic C/C++
look and feel), I am toying with the thought of making a tiny
idiomatic Lua module for just the things from s2geometry that I need.
But if somebody already has something of the kind, I'll be glad to
hear about it.