站长说的很对，补充一下： hR%2[lBn!]
Normal Vector () %;s2>F
The Normal Vector is a vector in 3D space that is used to orient the projection Xo~kB)|,
plane for the irradiance map. The plane is defined to be perpendicular to the m00 5*>IY
Normal Vector, and the irradiance incident on the selected surface is projected `Fs- z
onto this plane. When the map is displayed, the normal vector is pointing toward _"'0^F$I
you. >J_%'%%f
Up Vector -%6Y&_5VK
The Up Vector is a vector in 3D space that is used to orient the projection plane :dj=kuUTbu
for the irradiance map. The plane is defined so that the Up Vector is parallel to the /D
~UK" }
vertical side of the plane. The irradiance incident on the selected surface is %] [6TZ}
projected onto this plane. When the map is displayed, the up vector will point b<"LUM*;
toward the top of the screen.
