@article{Bitterli15Portals,
    title   = {Portal-Masked Environment Map Sampling},
    author  = {Benedikt Bitterli and Jan Nov\'{a}k and Wojciech Jarosz},
    journal = {Computer Graphics Forum (Proc. of EGSR)},
    year    = {2015},
    volume  = {34},
    number  = {4},
    month   = jun,
}