站长说的很对，补充一下： 4dawg8K`9
Normal Vector q[3x2sR
The Normal Vector is a vector in 3D space that is used to orient the projection -d+aV1n
plane for the irradiance map. The plane is defined to be perpendicular to the 5%zXAQD=<
Normal Vector, and the irradiance incident on the selected surface is projected C NsNZJ
onto this plane. When the map is displayed, the normal vector is pointing toward @I`C#~
you. tZyo`[La
Up Vector &;i
"P
The Up Vector is a vector in 3D space that is used to orient the projection plane Jzkq)]M
for the irradiance map. The plane is defined so that the Up Vector is parallel to the S4UM| `
vertical side of the plane. The irradiance incident on the selected surface is q:\g^_!OGA
projected onto this plane. When the map is displayed, the up vector will point dS2G}L^L
toward the top of the screen.
