站长说的很对，补充一下： +&&MUT{
3
Normal Vector /1 [}G !
The Normal Vector is a vector in 3D space that is used to orient the projection z226yNlS
plane for the irradiance map. The plane is defined to be perpendicular to the 9n06n$F
Normal Vector, and the irradiance incident on the selected surface is projected ~(w=U *
onto this plane. When the map is displayed, the normal vector is pointing toward awj} K
you. LAu+{'O\
Up Vector nR=2eBNf
The Up Vector is a vector in 3D space that is used to orient the projection plane +An![1N,
for the irradiance map. The plane is defined so that the Up Vector is parallel to the zLJ:U`uh\
vertical side of the plane. The irradiance incident on the selected surface is [R@q]S/
projected onto this plane. When the map is displayed, the up vector will point <lg"M;&Ht
toward the top of the screen.
