站长说的很对，补充一下： EM& ;SQ;C9
Normal Vector yC <[ LH
The Normal Vector is a vector in 3D space that is used to orient the projection uEPdL':}2
plane for the irradiance map. The plane is defined to be perpendicular to the DeTD.)pS
Normal Vector, and the irradiance incident on the selected surface is projected \C(dWs
onto this plane. When the map is displayed, the normal vector is pointing toward 'HdOW[3o
you. ek3,ss3
Up Vector A(<"oAe|
The Up Vector is a vector in 3D space that is used to orient the projection plane ;x=r.3OQy
for the irradiance map. The plane is defined so that the Up Vector is parallel to the @rT}V>2I
vertical side of the plane. The irradiance incident on the selected surface is | N/Wu9w$
projected onto this plane. When the map is displayed, the up vector will point +zup+=0e
toward the top of the screen.
