@AllisonVacanti Thanks for that detailed answer. I need it for for that class https://github.com/zippy84/vtkbool/blob/test/vtkPolyDataContactFilter.cxx. On very detailed meshes this part of the lib takes about 95% of the execution time. This is not a good rate. You gave a lot of information with your two links. I hope I can improve anything with it.
Any help is welcome 