站长说的很对,补充一下:
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Normal Vector CEjMHP$=
The Normal Vector is a vector in 3D space that is used to orient the projection FjD`bhw-
plane for the irradiance map. The plane is defined to be perpendicular to the e>\[OwF-x
Normal Vector, and the irradiance incident on the selected surface is projected V(n7hpS
onto this plane. When the map is displayed, the normal vector is pointing toward
`b 6j7
you. D9^.Eg8W
Up Vector #]pFE.o
The Up Vector is a vector in 3D space that is used to orient the projection plane Cc7PhoPK
for the irradiance map. The plane is defined so that the Up Vector is parallel to the '=}F}[d"kk
vertical side of the plane. The irradiance incident on the selected surface is Y8YNRyc=
projected onto this plane. When the map is displayed, the up vector will point [h20y
toward the top of the screen.