The Visualization Toolkit (VTK) is the open-source library underlying ParaView—it is a very efficient piece of software for everything related to geometry, images and meshes. After being a user for many years, Martin recently corrected some bugs related to the handling of second order tensors, and his patches are now part of the library's master branch, for everyone to use. More info here.
Inria/École Polytechnique joint research team