Tesseroids is a collection of command-line programs for modeling the gravitational potential, acceleration, and gradient tensor. Tesseroids supports models and computation grids in Cartesian and spherical coordinates.
The geometric element used in the modeling processes is a spherical prism, also called a tesseroid. Tesseroids also contains programs for modeling using right rectangular prisms, both in Cartesian and spherical coordinates.
I started working on Tesseroids in 2008 for my Bachelor's degree thesis. Since then, the software has been through many revisions.
The paper "Tesseroids: forward modeling gravitational fields in spherical coordinates" describes the algorithms behind version 1.2.0 of the software. This paper became a chapter of my PhD thesis.