站长说的很对，补充一下： <~TP#uAz
Normal Vector /-bF$)vN
The Normal Vector is a vector in 3D space that is used to orient the projection %*aJLn+]_R
plane for the irradiance map. The plane is defined to be perpendicular to the LE5.b]tv2
Normal Vector, and the irradiance incident on the selected surface is projected :@W. K5
onto this plane. When the map is displayed, the normal vector is pointing toward iv`O /T
you. ;6@r-r
Up Vector V.ht,
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The Up Vector is a vector in 3D space that is used to orient the projection plane F' U 50usV
for the irradiance map. The plane is defined so that the Up Vector is parallel to the y@2epY?{
vertical side of the plane. The irradiance incident on the selected surface is dzK{
Z
projected onto this plane. When the map is displayed, the up vector will point b| Q)[ y]
toward the top of the screen.
