I am using GLSL 1.5 trying to calculate per vertex lighting, and my problem is I do not really know how to calculate the normal for every vertex. Should I do it in vertex shader or I should do it in main OpenGL program and pass this value into the shader. In previous version there was gl_Normal defined value which is deprecated in 1.5 version. I will be very happy if someone can explain me this.
Thank you for help.