SB-CGA is a computer graphics algebra library for Common Lisp.
Despite the prefix it is actually portable - but optimizations that make it fast (using SIMD instructions) are currently implemented for SBCL/x86-64 only.
There is no fundamental reason why these could not be implemented for other implementations as well, though.
SB-CGA is not under active development currently, but neither is it quite abandoned. Patches will get looked at, though you may need to kick Nikodemus once or twice to get his attention.
There's a manual: http://nikodemus.github.io/sb-cga/
There's a TODO in TODO.org.
There's a pending re-implementation of the root solvers in new-roots.lisp.