@Article{Svoboda-Presence2005,
  author =		 {Svoboda, Tom{\'a}{\v s} and Martinec, Daniel and
                  Pajdla, Tom{\'a}{\v s}},
  title =		 {A Convenient Multi-Camera Self-Calibration for
                  Virtual Environments},
  journal =		 {PRESENCE: Teleoperators and Virtual Environments},
  publisher =	 {The MIT Press},
  address =		 {Cambridge MA},
  issn =		 {1054-7460},
  year =		 {2005},
  volume =		 {14},
  number =		 {4},
  pages =		 {407-422},
  month =		 {August},
  authorship =	 {60-30-10},
  project =		 {1ET101210407, IST-2001-39184, 1M6840770004, 1ET101210406, Dur IG2003-2 062, CONEX GZ 45.535},
  keywords =	 {camera calibration, selfcalibration, multicamera
                  calibration, virtual room, camera dome},
  note =		 {},
  annote =		 {Virtual immersive environments or telepresence
                  setups often consist of multiple cameras which have
                  to be calibrated. We present a convenient method for
                  doing this. The minimum is three cameras, but there
                  is no upper limit. The method is fully automatic and
                  a freely moving bright spot is the only calibration
                  object. A set of virtual 3D points is made by waving
                  the bright spot through the working volume. Its
                  projections are found with sub-pixel precision and
                  verified by a robust RANSAC analysis. The cameras do
                  not have to see all points, only reasonable overlap
                  between camera subgroups is necessary. Projective
                  structures are computed via rank-4 factorization and
                  the Euclidean stratification is done by imposing
                  geometric constraints. This linear estimate
                  initializes a post-processing computation of
                  non-linear distortion which is also fully
                  automatic. We suggest a trick on how to use a very
                  ordinary laser pointer as the calibration object. We
                  show that it is possible to calibrate an immersive
                  virtual environment with 16 cameras in less than 30
                  minutes reaching about 1/5 pixel reprojection
                  error. The method has been successfully tested on
                  numerous multi-camera environments with a varying
                  number and quality of cameras used.},
}