站长说的很对，补充一下： yGBQ0o7E
Normal Vector +YY8h>hj
The Normal Vector is a vector in 3D space that is used to orient the projection cc=gCE
plane for the irradiance map. The plane is defined to be perpendicular to the "bQ[ CD
Normal Vector, and the irradiance incident on the selected surface is projected fG LG$b
onto this plane. When the map is displayed, the normal vector is pointing toward 0X|_^"!
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Up Vector .Ce8L& cU
The Up Vector is a vector in 3D space that is used to orient the projection plane \ 0;(VLN'U
for the irradiance map. The plane is defined so that the Up Vector is parallel to the R,2=&+ e
vertical side of the plane. The irradiance incident on the selected surface is &[R8Q|1 j
projected onto this plane. When the map is displayed, the up vector will point ;^u*hZN[Up
toward the top of the screen.
