站长说的很对,补充一下: {: W$LWET
Normal Vector ~;] d"'
The Normal Vector is a vector in 3D space that is used to orient the projection @|)Z"m7
plane for the irradiance map. The plane is defined to be perpendicular to the P>6{&(
Normal Vector, and the irradiance incident on the selected surface is projected 5:Uso{
onto this plane. When the map is displayed, the normal vector is pointing toward F<w/PMb
you. y!%CffF2
Up Vector 3mni>*q7d
The Up Vector is a vector in 3D space that is used to orient the projection plane h1(4Ic
for the irradiance map. The plane is defined so that the Up Vector is parallel to the A(N4N
vertical side of the plane. The irradiance incident on the selected surface is (9h`3#
projected onto this plane. When the map is displayed, the up vector will point GH
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toward the top of the screen.