站长说的很对,补充一下: [`lAc V<
Normal Vector '9gI=/29D
The Normal Vector is a vector in 3D space that is used to orient the projection ~83P09\T%
plane for the irradiance map. The plane is defined to be perpendicular to the (r4\dp&
Normal Vector, and the irradiance incident on the selected surface is projected SJ-Sac58r
onto this plane. When the map is displayed, the normal vector is pointing toward ,L;vN6~
you. 5dk,!Cjg
Up Vector :Mk}Suf&H
The Up Vector is a vector in 3D space that is used to orient the projection plane =)8Ct
for the irradiance map. The plane is defined so that the Up Vector is parallel to the ._Xtb,p{
vertical side of the plane. The irradiance incident on the selected surface is wW4S@m
projected onto this plane. When the map is displayed, the up vector will point qu%s 7+
toward the top of the screen.