站长说的很对,补充一下: !3{;oU%*
Normal Vector u'^kpr`y
The Normal Vector is a vector in 3D space that is used to orient the projection j<k-w
plane for the irradiance map. The plane is defined to be perpendicular to the vpC?JXz=H
Normal Vector, and the irradiance incident on the selected surface is projected biS{.
onto this plane. When the map is displayed, the normal vector is pointing toward Y ` Z,52
you. nX\mCO4T
Up Vector R:rols"QM
The Up Vector is a vector in 3D space that is used to orient the projection plane X]o"vx%C
for the irradiance map. The plane is defined so that the Up Vector is parallel to the UY .-Qt
vertical side of the plane. The irradiance incident on the selected surface is j<R&?*
projected onto this plane. When the map is displayed, the up vector will point XM#nb$gl
toward the top of the screen.