站长说的很对,补充一下: 7rdw`
Normal Vector "X5_-l
The Normal Vector is a vector in 3D space that is used to orient the projection ;V~rWzKM(
plane for the irradiance map. The plane is defined to be perpendicular to the e?!L}^f6X
Normal Vector, and the irradiance incident on the selected surface is projected If-,c^i
onto this plane. When the map is displayed, the normal vector is pointing toward &]VQR2J}:
you. 7?MB8tJ5r4
Up Vector `c'
The Up Vector is a vector in 3D space that is used to orient the projection plane %GX uuE}mX
for the irradiance map. The plane is defined so that the Up Vector is parallel to the g8I!E$
vertical side of the plane. The irradiance incident on the selected surface is DikdC5>O>m
projected onto this plane. When the map is displayed, the up vector will point \TbsoWX
toward the top of the screen.