Benjamin Resch Jian Wei Hendrik P. A. Lensch Real Time Direct Visual Odometry for Flexible Multi-camera Rigs. 503-518 2016 ACCV (4) https://doi.org/10.1007/978-3-319-54190-7_31 conf/accv/2016-4 db/conf/accv/accv2016-4.html#ReschWL16