站长说的很对，补充一下： *_ U=KpZF
Normal Vector "PK`Ca@`v
The Normal Vector is a vector in 3D space that is used to orient the projection fz[-pJ5[
plane for the irradiance map. The plane is defined to be perpendicular to the tO@n3"O
Normal Vector, and the irradiance incident on the selected surface is projected fF|m~#y
onto this plane. When the map is displayed, the normal vector is pointing toward 1MPn{#F f
you. z6Xn9
Up Vector q-3e^-S*
The Up Vector is a vector in 3D space that is used to orient the projection plane ta*6xpz-\Q
for the irradiance map. The plane is defined so that the Up Vector is parallel to the Pf,lZU?f
vertical side of the plane. The irradiance incident on the selected surface is Qy!;RaA3T
projected onto this plane. When the map is displayed, the up vector will point s"x iGp9
toward the top of the screen.
