Hi,
To make a polygon with the lighting effect on its both faces, Do we draw it two times, in each of which we set a proper normal? The two normals are opposite to each other.
Is there a better way? Please help. Thanks.
TOny
What you want is two sided lighting.
See glLightModel with GL_LIGHT_MODEL_TWO_SIDE.
Nvidia have some demos of this but I am unsure how fast this is on other cards. (you may be better off doing a double render)