站长说的很对，补充一下： u JH[C>
Normal Vector w1-P6cf
The Normal Vector is a vector in 3D space that is used to orient the projection +'5I8FE-
plane for the irradiance map. The plane is defined to be perpendicular to the 8kdJtEW3
Normal Vector, and the irradiance incident on the selected surface is projected vK+ re XE
onto this plane. When the map is displayed, the normal vector is pointing toward O<V 4j ,
you. >"=DN5w
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Up Vector flC%<V%'-
The Up Vector is a vector in 3D space that is used to orient the projection plane N8Z z6{rp
for the irradiance map. The plane is defined so that the Up Vector is parallel to the *-Yw%uR
vertical side of the plane. The irradiance incident on the selected surface is x> ## qYT
projected onto this plane. When the map is displayed, the up vector will point RzL(Gnb
toward the top of the screen.
