double sided lighting

OpenGL OpenGL: Basic Coding
1

hi,

  1. can someone tell me how i code double sided normals which point to both directions on its axis ?

  2. how do i change the shading model for both sides of a polygon? when i draw a bezier mesh with flat shading , one side is flat shaded (i think its the front) and the other side is smooth shaded.

thanks

2
  1. Search for the terms ‘cross product’. This is how you compute the normals of a object. Once you compute the normals going in one direction perpendicular to the object in question it should be easy to calculate the opposite normals by simply negating them.