Kun Zhou et al., "Analytic Double Product Integrals for All-Frequency Relighting," in IEEE Transactions on Visualization & Computer Graphics, vol. 19, no. , pp. 1133-1142, 2013.
doi:10.1109/TVCG.2012.152
keywords:{Lighting;Integral equations;Piecewise linear approximation;Computer graphics;Real time systems;Linear approximation;all frequency relighting;Analytic double product integral},
url:doi.ieeecomputersociety.org/10.1109/TVCG.2012.152