站长说的很对,补充一下: EX4
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Normal Vector b_vVB`>
The Normal Vector is a vector in 3D space that is used to orient the projection ge$LIsE8
plane for the irradiance map. The plane is defined to be perpendicular to the Y#`Lcg+r,
Normal Vector, and the irradiance incident on the selected surface is projected ".E5t@ }?m
onto this plane. When the map is displayed, the normal vector is pointing toward {S*!B
you. izf~w^/
Up Vector 7 W{~f?Sh
The Up Vector is a vector in 3D space that is used to orient the projection plane S*g`d;8gV
for the irradiance map. The plane is defined so that the Up Vector is parallel to the %9X{{_
vertical side of the plane. The irradiance incident on the selected surface is g#qNHR
projected onto this plane. When the map is displayed, the up vector will point =53bLzr
toward the top of the screen.