站长说的很对，补充一下： bbNN$-S|
Normal Vector g&&-
The Normal Vector is a vector in 3D space that is used to orient the projection 8/gA]I
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plane for the irradiance map. The plane is defined to be perpendicular to the q8 &\;GK|
Normal Vector, and the irradiance incident on the selected surface is projected :#nfdvqm
onto this plane. When the map is displayed, the normal vector is pointing toward 7up~8e$ _
you. Oz{FM6
Up Vector TF_wT28AU2
The Up Vector is a vector in 3D space that is used to orient the projection plane U\y:\+e l
for the irradiance map. The plane is defined so that the Up Vector is parallel to the wHuz~y6
vertical side of the plane. The irradiance incident on the selected surface is p`qy57
projected onto this plane. When the map is displayed, the up vector will point 2y `X)
toward the top of the screen.
