fix of the light.co ceres.dll
see here for description on how/what
http://ceres-solver.org/installation.html but since i'm using the windows version i grabbed this build, (using submodules to get glog)
https://github.com/tbennun/ceres-windows it needs Eigen
http://eigen.tuxfamily.org/index.php?title=Main_Page grabbed 3.3.4 of Eigen, extracted it to the same folder as the ceres-2015.sln file and then renamed it to eigen
next opened the ceres-2015.sln in visual studio 2015, selected release and x64 build, built it and copied the ceres.dll to the lumen.exe folder. after making a backup of the old non working one.