III.3.5 Brief History
The basic concepts of beam-tracing were presented by Stephenson in 1996 [1], but the first functional implementation was published by Funkhouser et al in 1998 [2], [3]. The improved image-source technique by Mechel has similar approach than beam-tracing, but it still is closer to the original image-source technique [4]. Further optimization on the technique has been presented e.g. by Laine et al [5].