Akio Doi Takayuki Itoh Acceleration radiosity solutions through the use of hemisphere-base formfactor calculation. 3-15 1998 9 Journal of Visualization and Computer Animation 1 db/journals/jvca/jvca9.html#DoiI98 http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1099-1778(199801/03)9:1<3::AID-VIS171>3.0.CO;2-8/abstract