ligjt

Hi I have a cube without a face (this permit me to see inside it). the hole in the cube in in front of mine: I put face normals like
faceup (0,1,0), face left (-1,0,0)…now I have the light on the left of cube; beside faceLeft; it happen that inside cube all face appear dark/black (I think it’s ok). but the leftFace (inside) appear white (the color of cube faces). WHy? there isn’t a normal in inside cube and there isn’t a light…thanks

a light source is never occluded by the geometry, even though it may be occluded in reality. only the dot product of a face normal and the vector to the light source is taken into account.

to get the effect you want, you’ll need some kind of shadow algorithm.

Piece of code could be usefull … but seems you lights your cube from the righ side, not from the left and have two sided lighting enabled - the left side from outside is dark, isn’t it?

ok, so my face (a quads) must appear white in both sides…:!?? My light is positional, but i think this doens’t matter…

No, only from side where the light is. If you have e.g. quad on XZ plane (Y=0)and vertex normals are set up (0.0, 1.0, 0.0):
(front side (FS) is the side from where the normal comes out, back side (BS) is the other)

  1. you have one side lighting
    a)light is e.g. on position 0,10,0
    ->the FS will be lit
    b)light is e.g. on position 0,-10,0
    ->nothing will be lit
  2. you have two-sided lighting
    a)light is e.g. on position 0,10,0
    ->the FS will be lit
    b)light is e.g. on position 0,-10,0
    ->the BS will be lit