站长说的很对，补充一下： ~,^pya
Normal Vector :)9CG!2y<M
The Normal Vector is a vector in 3D space that is used to orient the projection SEKR`2Zz,
plane for the irradiance map. The plane is defined to be perpendicular to the 7 sX#6`t
Normal Vector, and the irradiance incident on the selected surface is projected $^TxLv
onto this plane. When the map is displayed, the normal vector is pointing toward et`1#_o
you. @2 3?II$=@
Up Vector B~ ?R 6
The Up Vector is a vector in 3D space that is used to orient the projection plane "]SA4Ud^
for the irradiance map. The plane is defined so that the Up Vector is parallel to the $)Y a lZ
vertical side of the plane. The irradiance incident on the selected surface is SO|!x}GfI
projected onto this plane. When the map is displayed, the up vector will point q1^bH 6*fl
toward the top of the screen.
