站长说的很对，补充一下： +j _ ;(Gw7
Normal Vector .~A*=
The Normal Vector is a vector in 3D space that is used to orient the projection v4,h&JLt
plane for the irradiance map. The plane is defined to be perpendicular to the MB^~%uZ2K
Normal Vector, and the irradiance incident on the selected surface is projected !) "%),>}o
onto this plane. When the map is displayed, the normal vector is pointing toward 1/ 1Xk,E
you. E907fX[R~
Up Vector ok^d@zI
The Up Vector is a vector in 3D space that is used to orient the projection plane z<sg0K8z63
for the irradiance map. The plane is defined so that the Up Vector is parallel to the :K`ESq!8u
vertical side of the plane. The irradiance incident on the selected surface is _/8FRk x
projected onto this plane. When the map is displayed, the up vector will point K5ZC:Ks
toward the top of the screen.
