請(qǐng)問(wèn)在照度圖設(shè)置Irradiance/Illuminance Maps當(dāng)中,有一項(xiàng)設(shè)置為“symmetry”,可以設(shè)置“l(fā)eft/right" "up/down”等,請(qǐng)問(wèn)在某些場(chǎng)合設(shè)置對(duì)稱(chēng)的目的是什么?設(shè)為"none"時(shí)照度圖不就是實(shí)際的照度圖嗎,設(shè)置為symmetry豈不是人為地變動(dòng)了照度結(jié)果?